Hydraulic actuator with on-demand energy flow

ABSTRACT

Various embodiments related to hydraulic actuators and active suspension systems as well as their methods of use are described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority under 35 U.S.C. § 119(e) of U.S.provisional application Ser. No. 61/789,600, entitled “ACTIVESUSPENSION” filed Mar. 15, 2013, U.S. provisional application Ser. No.61/815,251, entitled “ACTIVE SUSPENSION,” filed Apr. 23, 2013, U.S.provisional application Ser. No. 61/865,970, entitled “MULTI-PATH FLUIDDIVERTER VALVE,” filed Aug. 14, 2013, and U.S. provisional applicationSer. No. 61/930,452, entitled “ELECTROHYDRAULIC SYSTEMS”, filed Jan. 22,2014, the disclosures of which are incorporated by reference in theirentirety.

FIELD

Disclosed embodiments are related to the hydraulic actuation systems andcontrols.

BACKGROUND

Hydraulic actuators have long been used for motion control including,for example, active suspension systems which apply energy to the activesuspension in response to various loads applied to a wheel and/orassociated vehicle body. In order to achieve a desired level ofperformance, an active suspension system needs to have energy eitheralready present or capable of being provided at an appropriate time. Inthe case of hydraulic systems, the necessary energy corresponds to anecessary hydraulic pressure and flow. One common approach used inhydraulic actuation systems, as well as hydraulic active suspensionsystems, to ensure that energy is applied in a timely manner is to use acontinuously operating pump to provide a desired hydraulic pressure andflow. These types of systems control the fluid flow and pressureprovided by the continuously operating pump either by controlling thedisplacement of the pump and/or using one or more electronicallycontrolled valves to control the fluid flow and pressure from the pumpto the actuator. Some systems, especially systems including fixeddisplacement pumps, use valves to by-pass the actuator. However, itshould be noted that in some hydraulic systems, a speed of the pump maybe adjusted to increase or decrease the hydraulic flow volume and/orpressure.

Hydraulic actuator systems and hydraulic suspension systems aretypically powered using a hydraulic actuator associated with a remotelylocated hydraulic power source used to transfer hydraulic fluid to andfrom the actuator via an arrangement of hydraulic hoses or tubes.Hydraulic power sources may include various components including, forexample, an electric motor and pump assembly as well as a fluidreservoir.

SUMMARY

In one embodiment, an active suspension system includes a hydraulicactuator including an extension volume and a compression volume. Thehydraulic actuator is constructed and arranged to be coupled to avehicle wheel or suspension member. A hydraulic motor is in fluidcommunication with the extension volume and the compression volume ofthe hydraulic actuator to control extension and compression of thehydraulic actuator. An electric motor is also operatively coupled to thehydraulic motor. A controller is electrically coupled to the electricmotor, and the controller controls a motor input of the electric motorto operate the hydraulic actuator in at least three of four quadrants ofa force velocity domain of the hydraulic actuator.

In another embodiment, a method for controlling an active suspensionsystem includes: controlling a motor input of an electric motor tooperate a hydraulic actuator in at least three of four quadrants of aforce velocity domain of the hydraulic actuator, wherein the hydraulicactuator is constructed and arranged to be coupled to a vehicle wheel orsuspension member, and wherein the electric motor is operatively coupledto a hydraulic motor in fluid communication with an extension volume anda compression volume of the hydraulic actuator to control extension andcompression of the hydraulic actuator.

In yet another embodiment, an active suspension system includes ahydraulic actuator including an extension volume and a compressionvolume. The hydraulic actuator is constructed and arranged to be coupledto a vehicle wheel or suspension member. A hydraulic motor-pump is influid communication with the extension volume and the compression volumeof the hydraulic actuator to control extension and compression of thehydraulic actuator. An electric motor is also operatively coupled to thehydraulic motor, and a sensor is configured and arranged to sense wheelevents and/or body events. A controller is electrically coupled to theelectric motor and the sensor. Additionally, in response to a sensedwheel event and/or a sensed body event, the controller applies a motorinput to the electric motor to control the hydraulic actuator.

In another embodiment, a method for controlling an active suspensionsystem includes: sensing a wheel event and/or a body event; and applyinga motor input to an electric motor in response to the sensed wheel eventand/or the body event, wherein the electric motor is operatively coupledto a hydraulic motor-pump in fluid communication with an extensionvolume and a compression volume of a hydraulic actuator.

In yet another embodiment, an actuation system includes a hydraulicactuator including an extension volume and a compression volume. Ahydraulic motor is in fluid communication with the extension volume andthe compression volume of the hydraulic actuator to control extensionand compression of the hydraulic actuator. Also, an electric motor isoperatively coupled to the hydraulic motor. The actuation system has areflected system inertia and a system compliance, and a product of thesystem compliance times the reflected system inertia is less than orequal to about 0.0063 s⁻².

In another embodiment, a device includes a housing including a firstport and a second port. A hydraulic motor-pump is disposed within thehousing, and the hydraulic motor-pump controls a flow of fluid betweenthe first port and the second port. An electric motor is disposed withinthe housing and operatively coupled to the hydraulic motor.Additionally, a controller electrically coupled to the electric motorand disposed within the housing controls a motor input of the electricmotor.

In yet another embodiment, an active suspension system includes anactive suspension housing, and a hydraulic motor-pump disposed withinthe active suspension housing. The hydraulic motor controls a flow offluid through the active suspension housing. An electric motor isdisposed within the active suspension housing and operatively coupled tothe hydraulic motor. Also, a controller is electrically coupled to theelectric motor and disposed within the active suspension housing. Thecontroller controls a motor input of the electric motor.

In another embodiment, a vehicle includes one or more active suspensionactuators, where each active suspension actuator includes a hydraulicactuator including an extension volume and a compression volume. Ahydraulic motor-pump is in fluid communication with the extension volumeand the compression volume of the hydraulic actuator to controlextension and compression of the hydraulic actuator. An electric motoris operatively coupled to the hydraulic motor-pump, and a controller iselectrically coupled to the electric motor. The controller controls amotor input of the electric motor to control the hydraulic actuator.

In another embodiment, a device includes a housing and a pressure-sealedbarrier located in the housing disposed between a first portion of thehousing and a second portion of the housing. The first portion isconstructed and arranged to be filled with a fluid subjected to avariable pressure relative to the second portion. Additionally, anelectrical feed-through passes from the first portion of the housing tothe second portion of the housing through the pressure-sealed barrier. Acompliant connection is electrically connected to the electricalfeed-through and is also electrically connected to a controller disposedon or within the housing.

It should be appreciated that the foregoing concepts, and additionalconcepts discussed below, may be arranged in any suitable combination,as the present disclosure is not limited in this respect. Further, otheradvantages and novel features of the present disclosure will becomeapparent from the following detailed description of various non-limitingembodiments when considered in conjunction with the accompanyingfigures.

In cases where the present specification and a document incorporated byreference include conflicting and/or inconsistent disclosure, thepresent specification shall control. If two or more documentsincorporated by reference include conflicting and/or inconsistentdisclosure with respect to each other, then the document having thelater effective date shall control.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures may be represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1 is an exemplary graph of a conventional semi-active suspensionforce/velocity range;

FIG. 2 is an exemplary graph of an active suspension using four-quadrantcontrol;

FIG. 3 is an exemplary graph of frequency-domain for various inputs andmotor control of an active suspension system;

FIG. 4 is a schematic representation of a hydraulic actuator;

FIG. 5 is a schematic representation of a hydraulic actuator integratedinto a vehicle suspension;

FIG. 6 is an exemplary block diagram of an active suspension system;

FIG. 7 is an exemplary graph of an energy flow of an active suspensionsystem;

FIG. 8 is a graph of body acceleration and motor torque illustratingactive suspension control on a per-event basis;

FIG. 9 is a Bode diagram of frequency versus magnitude of torque commandcorrelated to body acceleration;

FIG. 10 is an exemplary block diagram of a feedback loop of an activesuspension system;

FIG. 11 is a calculated force response illustrating a response time, anovershoot, and subsequent force oscillation; and

FIG. 12 is a calculated Bode diagram.

FIG. 13 is a cross-sectional view of an active suspension actuatorincluding a hydraulic actuator and smart valve;

FIG. 14 is a cross-sectional view of a smart valve;

FIG. 15 is a cross-sectional view of an active suspension actuatorincluding a hydraulic actuator and smart valve;

FIG. 16 is an enlarged cross-sectional view of the smart valve of FIG.15;

FIG. 17 is a schematic representation of a controller-valve integration;

FIG. 18 is a schematic representation of a generic electro-hydraulicvalve architecture;

FIGS. 19A-19F depict various attachment methods for connecting a smartvalve to an actuator body;

FIG. 20 is a cross sectional view of a hydraulic actuator connected witha smart valve disposed in a wheel well at one corner of a vehicle;

FIG. 21 is a schematic representation of a hydraulic actuator connectedwith a smart valve disposed in the wheel well at one corner of a vehicleemploying a flex cable connection system;

FIG. 22 is a cross sectional view of a hydraulic actuator connected witha top mounted smart valve disposed in a wheel well at one corner of avehicle;

FIG. 23 is an exemplary block diagram of an active suspension withon-demand energy flow;

FIG. 24 is a schematic representation of an active suspension adapted toprovide on-demand energy;

FIG. 25 is a schematic representation of an active suspension with aseries spring and parallel damper adapted to provide on-demand energy;

FIGS. 26A-26D are schematic representations of an active suspensionincluding valves and dampers adapted to provide on-demand energy;

FIG. 27 is a schematic representation of an active suspension comprisinga single acting actuator adapted to provide on-demand energy; and

FIG. 28 is a graph of a four operational quadrant force velocity domainfor an active suspension system.

DETAILED DESCRIPTION

The inventors have recognized several drawbacks associated with typicalhydraulic actuator systems and hydraulic suspension systems. Morespecifically, the costs associated with hydraulic power systems usedwith typical hydraulic actuators and hydraulic suspension systems can beprohibitively expensive for many applications. Further, the packagingassociated with remotely located hydraulic power systems necessitatesthe use of multiple hydraulic hoses and/or tubing over relatively longlengths which can present installation challenges and reliabilityissues. Additionally, as noted above applications requiring energy to beconstantly available require the use of a continuously running pump.However, the inventors have recognized that requiring a pump tocontinuously operate requires energy to be applied to the pump even whenno hydraulic energy is actually needed thus decreasing systemefficiency. While some systems use variable displacement pumps toincrease efficiency of the system, the systems tend to be more expensiveand less reliable than corresponding systems using fixed displacementpumps which can limit their use for many applications. Additionally,systems which adjust the speed of the pump also face several technicalchallenges limiting their use including, for example, startup friction,rotational inertia, and limitations in their electronic control systems.

In view of the above, as well as other considerations, the inventorshave recognized the benefits associated with decentralizing a hydraulicsystem in order to provide self-contained or partially self-containedhydraulic actuation systems. For example, and as described in moredetail below, instead of including a remotely located hydraulic powersystem, a hydraulic power system, or some portion of a hydraulic powersystem, may be integrated with, or attached to, a hydraulic actuator.Depending on the particular construction, this may reduce or eliminatethe need for external hydraulic connections between the hydraulic powersystem and the hydraulic actuator. This may both provide increasedreliability as well as reduced installation costs and complexityassociated with the overall hydraulic system.

The inventors have also recognized the benefits associated withproviding a hydraulic actuator and/or an active suspension systemcapable of providing on demand power which may reduce energy consumptionsince it does not require continuously operating a pump. A hydraulicsystem capable of providing on demand power may include a hydraulicactuator body, a hydraulic motor-pump, an associated electric motoroperatively coupled to the hydraulic motor-pump, and a controller.Additionally, the hydraulic motor-pump may be operated in lockstep withthe hydraulic actuator such that energy delivery to the electric motormay rapidly and directly control a pressure applied to, and thusresponse of, the hydraulic actuator without the need for ancillaryelectronically controlled valves. A hydraulic system capable ofproviding on demand power may also reduce the complexity of a systemwhile providing a desired level of performance.

In addition to the above, the inventors have recognized the benefitsassociated with providing a hydraulic actuator and/or suspension systemcapable of being controlled at a sufficiently fast rate to enable thesystem to respond to individual events as compared to control in asystem based on average behavior over time. This may be especiallybeneficial in use for a vehicle suspension system responding toindividual wheel and/or body events which may enable enhanced vehicleperformance and comfort. Additionally, depending on the particularapplication, a hydraulic system may also provide control within three ormore quadrants of a force velocity domain as described in more detailbelow. However, it should be understood that the hydraulic system mayalso operate in one, two, or any appropriate number of quadrants of theforce velocity domain as the disclosure is not so limited.

In embodiments implementing the disclosed hydraulic actuator andsuspension systems, the inventors have recognized that a response timeto supply a desired force and/or displacement by the hydraulic systemmay be limited due to inherent delays associated with compliances andinertias various components in the system. Consequently, in embodimentswhere it is desired to have a particular response time, the inventorshave recognized that it may be desirable to design the compliances andinertias of a hydraulic system to enable a desired level of performanceas described in more detail below.

While issues with typical hydraulic actuators and suspension systems aswell as several possible benefits associated with various embodimentshave been noted, the embodiments described herein should not be limitedto only addressing the limitations noted above and may also provideother benefits as neither the disclosure nor the claims are limited inthis fashion.

For the purposes of this application, the term hydraulic motor-pump mayrefer to either a hydraulic motor or a hydraulic pump.

In one embodiment, a hydraulic system includes a hydraulic actuator, ahydraulic motor-pump, an electric motor, and an associated controller.The hydraulic actuator includes an extension volume and a compressionvolume located within the housing of the hydraulic actuator. Theextension volume and the compression volume are located on either sideof a piston constructed and arranged to move through an extension strokeand a compression stroke of the actuator. The hydraulic actuator housingmay correspond to any appropriate structure including, for example, ahydraulic actuator housing including multiple channels defined by one ormore concentric tubes. The hydraulic actuator is associated with ahydraulic motor-pump that is in fluid communication with the extensionvolume and the compression volume of the hydraulic actuator to controlactuation of the hydraulic actuator. More specifically, when thehydraulic motor-pump is operated in a first direction, fluid flows fromthe extension volume to the compression volume and the hydraulicactuator undergoes an extension stroke. Correspondingly, when thehydraulic motor-pump is operated in a second direction, fluid flows fromthe compression volume to the extension volume and the hydraulicactuator undergoes a compression stroke. Additionally, in at least someembodiments, the hydraulic motor-pump may operate in lockstep with thehydraulic actuator to control both extension and compression of thehydraulic actuator. It should be understood that any appropriatehydraulic motor-pump might be used including devices capable ofproviding fixed displacements, variable displacements, fixed speeds,and/or variable speeds as the disclosure is not limited to anyparticular device. For example, in one embodiment, the hydraulicmotor-pump may correspond to a gerotor.

As noted above, the hydraulic system also includes an electric motorwhich is operatively coupled to the hydraulic motor-pump. The electricmotor may either be directly or indirectly coupled to the hydraulicmotor-pump as the disclosure is not so limited. In either case, theelectric motor controls force applied to the hydraulic motor-pump.Further, depending on how the electric motor is controlled, thehydraulic motor-pump may either actively drive the hydraulic actuator orit may act as a generator to provide damping to the hydraulic actuatorwhile also generating energy that may either be stored for future use ordissipated. In instances where the electric motor is back driven as agenerator, the hydraulic motor-pump is driven in a particular directionby fluid flowing between the compression volume and the extension volumeof a hydraulic actuator in response to an applied force. In turn, thehydraulic motor-pump drives the electric motor to produce electricalenergy. By controlling an impedance, or other appropriate input, appliedto the electric motor during generation, the damping force applied tothe hydraulic actuator may be electronically controlled to provide arange of forces. In some embodiments, the hydraulic motor-pump isoperated in lockstep with the hydraulic actuator.

The above-noted controller is electrically coupled to the electric motorand controls a motor input of the electric motor in order to control aforce applied to the hydraulic actuator as well as the particular modeof operation. The motor input may correspond to any appropriateparameter including, for example, a position, a voltage, a torque, animpedance, a frequency, and/or a motor speed of the electric motor. Theelectric motor may be powered by any appropriate energy sourceincluding, for example external energy sources such as an external powersupply, a battery on a car, and other appropriate sources as well asinternal sources which might be integrated with a controller and/or ahydraulic actuator such as batteries, super capacitors, hydraulicaccumulators, flywheels, and other appropriate devices. In view of theabove, the pressure supplied to the hydraulic actuator may be controlledby the electric motor connected to the hydraulic motor-pump without theneed for separately controlled valves.

The hydraulic motor-pump may also be operated in a bidirectional manner,though embodiments in which the hydraulic motor-pump is only operated ina single direction is also possible through the use of appropriatevalving. In such an embodiment, a position of the hydraulic actuator maybe determined by a position of the electric motor. Consequently,depending on how the electric motor is controlled, the associatedhydraulic actuator may be held still, actively extended, or activelycompressed. Alternatively, the hydraulic actuator may be subjected toeither compression damping or extension damping as well. Thus, ahydraulic system constructed and operated as described above may be usedto control the hydraulic actuator in either direction without the use ofcomplex valving arrangements and power is only applied to the systemwhen needed as contrasted to a continuously operating pump. For example,in one specific embodiment, over half of the fluid pumped by thehydraulic motor-pump may be used to actuate a hydraulic actuator insteadof bypassing the actuator through one or more valves.

In instances where a hydraulic actuator is used in load holdingapplications, such as in off-highway lifting applications, forklifts,lift booms or robotics applications for example, it may be desirable toincorporate load holding valves to hydraulically lock the actuator inplace until the actuator is commanded to move. Load holding devices mayalso be desirable for safety and/or fail safe reasons. In oneembodiment, a load holding device is one or more load holding valves.These one or more load holding valves may either be passive in nature,e.g. pilot operated check valves, or they may be active such that theyrequire a control input, e.g. solenoid operated valves. In otherembodiments, the load holding device is a mechanical device constructedand arranged to lock the hydraulic actuator in place. For example, theload holding device may be a mechanical brake constructed and arrangedto grip the piston rod. In such an embodiment, the mechanical device maybe hydraulically, mechanically, and/or electrically deactivated when itis desired to move the hydraulic actuator. While several possible loadholding devices are described above, it should be understood that anyappropriate device capable of limiting and/or preventing actuation of ahydraulic actuator might be used.

While a specific embodiment is described above, it should be understoodthat embodiments integrating various types of valving and/or acontinuously operating pump are also possible as the disclosure is notso limited.

In one embodiment, a hydraulic actuation system and/or a suspensionsystem includes an electric motor, a hydraulic motor-pump (which may bea hydrostatic unit commonly referred to as an HSU), a hydraulicactuator, and a motor controller. Depending on the embodiment, thevarious ones of the above-noted components may be disposed in, orintegrated with, a single housing. Additionally, the electric motor andthe hydraulic motor-pump may be closely coupled to one another. Theability to combine the electric motor, hydraulic motor-pump, and motorcontroller into a compact, self-contained unit, where the electric motorand the hydraulic motor-pump are closely coupled on a common shaft mayoffer many advantages in terms of size, performance, reliability anddurability. In some embodiments, the motor controller has the abilityfor bi-directional power flow and has the ability to accurately controlthe motor by controlling either the motor voltage, current, resistance,a combination of the above, or another appropriate motor input. This maypermit the motor controller to accurately achieve a desired motor speed,position, and/or torque based upon sensor input (from either internalsensors, external sensors or combination both). The above combination ofelements may be termed a ‘smart valve’ as the unit can accuratelycontrol hydraulic flow and/or pressure in a bi-directional manner.Additionally, this control may be achieved without the need for separatepassive or actively controlled valves. Though embodiments in whichadditional valves may be used with the smart valve are alsocontemplated.

As noted above, an electric motor and hydraulic motor-pump within thesmart valve may be close coupled on a common shaft. Additionally, thesecomponents may be disposed in a common fluid-filled housing, therebyeliminating the need for shafts with seals. This may increase thevalve's durability and performance. Additionally, some embodiments asmart valve also includes an integrated electronic controller which maycombine both power and logic capabilities and may also include sensors,such as a rotary position sensors, accelerometers, or temperaturesensors and the like. Integrating the electronic controller into thesmart valve minimizes the distance between the controller power boardand the electric motor windings, thereby reducing the length of thepower connection between the electric motor and the power board sectionof the integrated electronic controller. This may reduce both power lossin the connection and electromagnetic interference (EMI) disturbancesfrom within the vehicle.

The combination of a smart valve and a hydraulic actuator into a singlebody unit may provide a sleek and compact design that offers multiplebenefits. For example, such an embodiment reduces integration complexityby eliminating the need to run long hydraulic hoses, improves durabilityby fully sealing the system, reduces manufacturing cost, improvesresponse time by increasing the system stiffness, and reduces loses bothelectrical and hydraulic from the shorter distances between components.Such a system also allows for easy integration with many suspensionarchitectures, such as monotubes, McPherson struts or air-springsystems. For ease of integration into the vehicle, it is desirable forthe integrated active suspension smart valve and hydraulic actuator tofit within the constraints of size and/or shape of typical passivedamper-based suspension systems. Therefore, in some embodiments a smartvalve is sized and shaped to conform to the size, shape, and form factorconstraints of a typical passive damper-based suspension system whichmay, among other things, permit the smart valve based actuator to beinstalled in existing vehicle platforms without requiring substantialre-design of those platforms.

According to one aspect a smart valve may include an electronic controlunit or controller, an electric motor operatively coupled to a hydraulicmotor-pump, and one or more sensors configured into a single unit. Thehydraulic motor-pump includes a first port and a second port. The firstport is in fluid communication with an extension volume of a hydraulicactuator and the second port is in fluid communication with acompression volume of the hydraulic actuator. In such an embodiment, thesmart valve may be controlled to create controlled forces in multiple(e.g., typically three or four) quadrants of a vehicle suspension forcevelocity domain, whereby the four quadrants of the force velocity domainof the hydraulic actuator correspond to compression damping, extensiondamping, active extension, and active compression. Various embodimentsof a smart valve are possible and may optionally include the itemsidentified above including a piston disposed within the hydraulicactuator. The piston is movably positioned between the first chamber anda second chamber within the actuator. The first chamber may be anextension volume and the second chamber may be a compression volume.

According to another aspect, a smart valve may again include acontroller, an electric motor, a hydraulic motor-pump, and one or moresensors. The smart valve may be operated by the electronic controller toprovide a motor output such as a desired speed or torque of the electricmotor by controlling a motor input of the electric motor such as thevoltage or current through the motor windings. This may create a torquethat resists rotation of the motor.

According to another aspect the controller may control an electric motorby a motor input of at least one of position, voltage, torque, impedanceor frequency. Additionally, the various components of a smart valve maybe disposed in or integrated with a single housing or body.Alternatively the controller, electric motor, and sensors may be housedin a housing that can be assembled to a housing for the hydraulicmotor-pump to facilitate communication among the active suspensionsystem components.

In another embodiment, a smart valve may include an electric motor,electric motor controller, and hydraulic pump in a housing. Depending onthe embodiment, the housing is fluid filled. An alternate configurationof a smart valve may include a hydraulic pump, an electric motor thatcontrols operation of the hydraulic pump, an electric motor controller,and one or more sensors in a single body housing. In yet anotherconfiguration of a smart valve, the smart valve may include an electricmotor, a hydraulic motor-pump, and a piston equipped hydraulic actuatorin fluid communication with the hydraulic motor-pump.

According to another aspect, a smart valve may be sized and shaped tofit in a vehicle wheel well. In such an embodiment, a smart valve mayinclude a piston rod disposed in an actuator body, a hydraulic motor, anelectric motor, and an electric controller for controlling the electricmotor. The smart valve may also include one or more passive valvesdisposed in the actuator body. The passive valves may either operate ineither series or parallel with the hydraulic motor.

According to another aspect, a smart valve incorporated into an activesuspension system may be configured so that the electronic controllerthat controls the electric motor is closely integrated with the smartvalve and/or electric motor. This may beneficially minimize the lengthof a high current path from the control electronics to the electricmotor.

According to another aspect, it may be desired to integrate one or moresmart valves and/or hydraulic actuators with a vehicle active suspensionsystem that controls all wheels of the vehicle. Such a system mayinclude a plurality of smart valves, each being disposed proximal to avehicle wheel so that each smart valve is capable of producingwheel-specific variable flow and/or pressure for controlling theassociated wheels. This may be accomplished by controlling the flow offluid through the smart valve. Similar to the above, the flow of fluidthrough the individual smart valves may be controlled using the electricmotor associated with the hydraulic motor-pump of each smart valve.Depending on the particular embodiment, it may be desirable for theelectric motor to be coaxially disposed with the hydraulic motor-pump.

While several possible embodiments of a smart valve are describedherein, it should be understood that a smart valve may be configured ina variety of other ways. Some exemplary ways may include: an electronicmotor controller integrated with a motor housing so that there are noexposed or flexing wires that carry the motor current to the motorcontroller; a smart valve's components that are fully integrated with orconnected to an actuator body or housing; a smart valve's componentsthat are integrated with our connected to a hydraulic shock absorberbody; a smart valve's electronics may be mounted to an actuator; ahydraulic pump and electric motor of a smart valve are disposed on thesame shaft; a smart valve that requires no hydraulic hoses; a hydraulicmotor that is roughly axially aligned with a piston rod of an actuator;a hydraulic motor that is roughly perpendicular to a piston rod traveldirection; as well as a smart valve that is mounted between the top of astrut and a lower control arm of a vehicle wheel assembly to name a few.

According to another aspect, particular applications a smart valve mayrequire particular size, shape, and/or orientation limitations.Exemplary smart valve embodiments for various applications are nowdescribed. In one embodiment, a smart valve is incorporated with asuspension and occupies a volume and shape that can fit within a vehiclewheel well and between the actuator top and bottom mounts. In anotherembodiment, smart valve integrated with a suspension and occupies avolume and shape such that during full range of motion and articulationof an associated actuator in the suspension system, adequate clearanceis maintained between the smart valve and all surrounding components. Inyet another embodiment, a suspension actuator supports a smart valveco-axially with the actuator body and connects to an actuator top mount.In another embodiment, a suspension actuator supports a smart valveco-axially with the actuator body and occupies a diameter substantiallysimilar to that of an automotive damper top mount and spring perch. Anactive suspension control of motor-pump may be configured to be lessthan 8 inches in diameter and 8 inches in depth, and even in some cases,substantially smaller than this footprint.

According to another aspect, a smart valve may be self-contained and maynot require externally generated knowledge, sensor input, or other datafrom a vehicle. A smart valve with an integrated processor-basedcontroller may function independently of other systems. This may includefunctions such as self-calibration regardless of whether there are othersmart valves (e.g. corner controllers) operating on other wheels of thevehicle. A smart valve may deliver a wide range of suspensionperformance which may include operating as a passive damper, asemi-active suspension/regenerative actuator, a variable suspension,and/or as a fully active suspension and the like. This functionality isfacilitated because it is self-contained and all of the required power,logic control, and all hydraulic connections are contained within theactuator assembly. A self-contained smart valve may be combined with awide range of advanced vehicle capabilities to deliver potentially morevalue and/or improved performance. Combining a smart valve withpredictive control, GPS enabled road condition information, radar,look-ahead sensors, and the like may be readily accomplished through useof a vehicle communication bus, such as a CAN bus. Algorithms in thesmart valve may incorporate this additional information to adjustsuspension operation, performance, and the like. In an example, if arear wheel smart valve had knowledge of actions being taken by a frontwheel smart valve and some knowledge of vehicle speed, the suspensionsystem of the rear wheel could be prepared to respond to a wheel eventbefore the wheel experiences the event.

According to another aspect, a flexible membrane, or compliantelectrical connections combined with other pressure sealed barriers, maybe used to mechanically decouple motion of the membrane or barrier froma controller located within a hydraulically pressurized housing. Thehydraulically pressurized housing may include a separate pressurizedfluid filled portion and an air filled portion. Decoupling the movementfrom the controller may help to prevent the braking of solder jointsbetween the motor connections passing through the membrane or pressuresealed barrier connected to the controller's printed circuit board.According to another aspect, co-locating a controller electronics withina hydraulically pressurized housing, also eliminates the need forcomplex mechanical feed-throughs and provides a more predictable thermalenvironment.

According to another aspect hydraulic pressure ripple from a hydraulicmotor-pump is reduced by using a rotary position sensor to supplysignals for a hydraulic ripple cancellation algorithm, and/or using aport timed accumulator buffer.

The above-described hydraulic actuation system may be used in any numberof applications. For example, a hydraulic system may be constructed andarranged to be coupled to an excavator arm, the control surfaces of anaircraft (e.g. flaps, ailerons, elevators, rudders, etc.), forklifts,lift booms, and active suspension systems to name a few. Therefore,while a specific embodiment of a control system directed to an activesuspension system as described in more detail below, it should beunderstood that the noted control methods and systems described belowmay be integrated into any appropriate system and should not be limitedto only an active suspension system.

FIGS. 1 and 2 present plots of various ways to control a hydraulicactuator integrated into a suspension system within a force velocitydomain. As illustrated in the figure, the force velocity domain includesa first quadrant I corresponding to extension damping where a force isapplied by the hydraulic actuator to counteract extension of hydraulicactuator. Similarly, quadrant III corresponds to compression dampingwhere a force is applied by the hydraulic actuator to counteractcompression of the hydraulic actuator a compressive force. In contrast,quadrants II and IV correspond to active compression and activeextension of the hydraulic actuator where it is driven to a desiredposition.

FIG. 1 is a representative plot of the command authority 2 of anactuator integrated into a typical semi-active suspension. Asillustrated in the figure, the command authority 2 of the semi-activesuspension is located within quadrants I and III corresponding toextension and compression damping. Therefore, such a system only appliesforces to counteract movement (i.e. reactive forces). Typically,performance of a semi-active suspension may be varied between dampingcharacteristic curves corresponding to full soft 4 and full stiffness 6through opening and closing of a simple electronically controlled valveto regulate fluid flow through the system. Systems incorporatingelectrically controlled valves typically consume energy in order tooperate and energy associated with damping of the hydraulic actuator isdissipated as heat. In addition, the operating range of a semi-activesystem is limited due to leakage at high forces and would be subject tofluid losses and frictional effects at lower forces.

A hydraulic actuator as described herein might be operated to emulatethe performance of a semi-active system as shown in FIG. 1. However,such a system would regenerate energy instead of consuming energy. Forexample, if the terminals of an electric motor operatively coupled to ahydraulic motor-pump were left in an open circuit state (e.g. arelatively high impedance state), a damping curve similar to the fullsoft 4 curve may be achieved. If instead the terminals of the electricmotor were connected to a low impedance, a damping curve similar to thefull stiff 6 curve may be achieved. For damping curves between thesebounds, a hydraulic actuator such as those described herein may generateenergy from wheel movement. Description of the high and low impedancestates is a functional description; in some embodiments this may beachieved with a switching power converter such as an H-bridge motorcontroller, where the switches are controlled to achieve the desiredtorque characteristic. However, it should be understood that anyappropriate mechanism capable of controlling the applied impedance orother appropriate motor input might be used. In either case, the outputtorque even in a semi-active mode may be controlled in direct responseto a wheel event to create force only when necessary and without theneed to continuously provide energy to the system from a continuouslyoperating pump.

While it may be possible to emulate the performance of a semi-activesuspension system, in some embodiments it is desirable to operate ahydraulic actuator in a full active mode. In such an embodiment, acontroller associated with an electric motor controls an input of theelectric motor in order to provide controlled forces using the hydraulicactuator in at least three quadrants of the force velocity domain asdescribed in more detail below. However, in at least one embodiment, thehydraulic actuator may be operated to create a controlled force in allfour quadrants as the disclosure is not so limited.

FIG. 2 is a representative plot of the command authority 8 of ahydraulic actuator incorporated into a full active suspension system. Inthe first quadrant I, the system is able to provide extension dampingwhich might correspond to a reactive force to rebound of a vehiclewheel. In the third quadrant III the system is able to providecompression damping which might correspond to a reactive force tocompression of a vehicle wheel. As previously described, a hydraulicsystem may be adapted to generate energy in at least part of quadrants Iand III though embodiments in which this energy is dissipated are alsopossible. However, unlike the semi-active systems described above, thesystem is also able to create a force in at least one of the tworemaining quadrants corresponding to active compression II which mightcorrespond to applying a force to pull a vehicle wheel up and/or activeextension IV which may correspond to applying a force to push a wheeldown. In these quadrants, the system may consume energy to apply thedesired force. This energy may come from any appropriate sourceincluding, for example: electrical energy from a vehicle or energystorage device such as a capacitor or battery; hydraulic energy storagefrom devices such as an accumulator or similar device; and/or mechanicalmeans of energy storage such as a flywheel.

In light of the above description, in some embodiments a full activesystem operated in at least three of the four quadrants of a forcevelocity domain provides bidirectional energy flow. More specifically,in quadrants I and III energy is regenerated by the electric motor beingdriven during compression damping and extension damping, and inquadrants II and IV energy is applied to and consumed by the electricmotor to actively extend or compress the hydraulic actuator. Such ahydraulic actuation system may be particularly beneficial as compared toprevious hydraulic actuation systems integrated with a suspension systembecause it does not require the use of separate actively controlledvalves to control the flow of fluid to and from various portions of thehydraulic actuator body.

While embodiments of a hydraulic actuator as described herein arecapable of operating in all four quadrants of the force velocity domain,as noted above, the energy delivered to the hydraulic actuator iscontrolled by the force, speed and direction of operation of theelectric motor and hydraulic motor-pump. More specifically, the electricmotor and the hydraulic motor-pump as well, as well as other associatedcomponents, continuously reverse operation directions, accelerate fromone operation speed to another, and go from a stop to a desiredoperation speed throughout operation of the hydraulic actuator.Consequently, a response time of the hydraulic actuator will includedelays associated with the ability of these various components toquickly transition between one operation state and the next. This is incomparison to systems that simply open and close valves associated witha hydraulic line including a constant flow of fluid and/or pressure tocontrol an associated hydraulic actuator. Therefore, in someembodiments, it is desirable to design a system to provide a desiredresponse time in order to achieve a desired system performance whiletaking into account response delays associated with other devices aswell. While several types of events are noted above, it should beunderstood that other types of behavior associated with operation of theelectric motor and the hydraulic motor-pump are also possible.

While a fast response time is desirable in any number of applications,as described in more detail below, in one embodiment a system includingan associated hydraulic actuator, electric motor, and hydraulicmotor-pump is designed with a sufficiently fast response time in orderto function in an active suspension system. In such an embodiment, theresponse time may be selected such that the active suspension system iscapable of responding to individual events. While these events maycorrespond to any appropriate control input, in some embodiments, theseevents are individual body events and/or wheel events. In one suchembodiment, a sensor is configured and arranged to sense wheel eventsand/or body events of a vehicle. The sensor is electrically coupled tothe controller of a hydraulic actuator integrated into a suspensionsystem. Upon sensing a wheel event and/or a body event, the controllerapplies a motor input to the electric motor which is coupled to thehydraulic motor-pump. This in turn directly controls the flow of fluidwithin the hydraulic actuator as the hydraulic motor-pump applies aforce to the hydraulic actuator. Therefore, the hydraulic actuator isable to be controlled in response to the individual sensed wheel eventsand/or body events that result in either wheel or body movement. Asdescribed in more detail below, individual body events and/or wheelevents typically occur at frequencies greater than 0.5 Hz, 2 Hz, 8 Hz,or any other appropriate frequency. Individual body events and/or wheelevents also typically occur at frequencies less than about 20 Hz.Therefore, in one embodiment, a hydraulic actuation system integratedinto a suspension system is engineered to respond to individual bodyevents and/or wheel events occurring at frequencies between about 0.5 Hzto 20 Hz inclusively.

In view of the rate at which individual body events and/or wheel eventsoccur, in some embodiments, it is desirable that a response time of thehydraulic system be at least equivalent in time to these events. In someembodiments, it may be desirable that the response time is faster thanthe rate at which individual events occur due to other delays present inthe system which may be taken into account when responding to individualevents. In view of the above, in some embodiments, a response time ofthe hydraulic system may be less than about 150 ms, 100 ms, 50 ms, orany other appropriate time period. The response times may also begreater than about 1 ms, 10 ms, 20 ms, 50 ms, or any other appropriatetime period. For example, a response time of the hydraulic system may bebetween about 1 ms and 150 ms, 10 ms and 150 ms, 10 ms and 100 ms, or 10ms and 50 ms. It should be understood that response times greater thanor less than those noted above are also possible. Additionally, itshould be understood that hydraulic actuators exhibiting fast responsetimes such as those noted above may be used in applications other than asuspension system as the disclosure is not limited to any particularapplication.

As described in more detail in the examples, and without wishing to bebound by theory, the response time of a hydraulic actuation system isproportional to the natural frequency of the hydraulic actuation system.Therefore, in order to provide the desired response times, a naturalfrequency of the hydraulic actuation system may be greater than about 2Hz, 5 Hz, 10 Hz, 20 Hz, or any other appropriate frequency.Additionally, the natural frequency may be less than about 100 Hz, 50Hz, 40 Hz. For example, in one embodiment, the natural frequency of thehydraulic actuation system is between about 2 Hz and 100 Hz inclusively.

Without wishing to be bound by theory, design considerations that impactthe natural frequency of a hydraulic actuation system include thereflected inertia as well as the compliance of the hydraulic actuationsystem. As noted in the examples, the natural frequency of the hydraulicactuation system may be defined using the formula:

${2\pi\; f} = \sqrt{\frac{K}{J\; n^{2}}}$

where f is the natural frequency of the hydraulic actuation system, 1/Kis the total compliance of the hydraulic actuation system, J is thetotal hydraulic actuation system inertia, and n is the motion ratio ofthe hydraulic actuation system. The quantity Jn² is the hydraulicactuation system reflected inertia.

A hydraulic actuation system's reflected inertia Jn² includes the rotarymoment of inertia J of all the components rotating in lockstep with themotion of the actuator, multiplied by the square of the motion ratio ntranslating rotation of the electric motor into linear motion of theactuator. For example, the reflected inertia can include the moment ofinertia of: the rotor; the coupling shaft between the electric motor andhydraulic motor-pump; any bearings coupled with the rotor, shaft, and/orpump; the hydraulic motor-pump; as well as other appropriate components.In one embodiment, the motion ratio n in a hydraulic actuation system asdescribed herein is characterized by the annular area of the pistonaround the piston rod in the hydraulic piston, divided by thedisplacement volume of the hydraulic motor-pump per revolution. However,other ways of defining the motion ratio n as would be known in the artare also contemplated. In a system where linear motion is prevalent, orwhere the transmission components moving linearly in response toactuation of the hydraulic motor-pump have significant mass, the totalreflected inertia may also include the mass of the linearly movingcomponents.

The total quantity Jn² can also be composed of multiple componentsmoving in lockstep with the motion of the piston, each with their ownrotating moment of inertia and their own transmission ratio n. Forexample, a bearing system constraining the in-plane motion of the motorshaft has components that rotate at a different angular velocities fromthat of the motor shaft. Depending on their total contribution to thereflected system inertia, it may be desirable to include thesecontributions in the reflected system inertia used for the design of thesystem using their respective moments of inertia and transmissionratios. For example, and without wishing to be bound by theory, if thebearing system is a roller type bearing, then the rollers will move inlockstep with the shaft but at an angular velocity that is close to halfthat of the shaft itself. At the same time, the individual rollers moveat a much faster angular velocity, while still in lockstep with theshaft. Thus each of these components may be accounted for using theirown moments of inertia and their own motion ratios.

In a system where linear motion is prevalent, and where the transmissionbetween actuation force and motor force uses a linear lever, the linearmass of the moving components in the motor may also be accounted forthrough their linear motion ratio n translating motion at the actuatorend to motion at the motor end of the lever. In this sense, theexpression Jn² is intended more generally as the sum of all the rotatingmoments of inertia and all the moving masses, each multiplied by thesquare of the motion ratio translating the linear or rotary motion atthe actuator into linear or rotary motion of the particular movingelement.

The hydraulic actuation system compliance 1/K is the compliance of allthe elements that are in series with the electric motor and locatedbetween the electric motor and a force output point of the hydraulicactuator (e.g. the moving shafts of the actuator). Various contributionsto the hydraulic actuation system compliance can include: a totalcompressibility of a fluid column between the hydraulic motor-pump and apiston of the hydraulic actuator; a flexibility of the hoses, tubes, orstructures connecting the hydraulic motor-pump to the hydraulicactuator; a flexibility of the mounting surfaces of the hydraulicactuator to a force application point; and other appropriateconsiderations which may contribute to the total compliance of thehydraulic actuation system. It should be noted that an inverse of thehydraulic actuation system compliance is the hydraulic actuation systemstiffness K.

In view of the above, in order to provide the desired naturalfrequencies, and thus response times, a hydraulic actuation system maybe designed using the interplay between the compliance and reflectedinertia. More specifically, a product of the reflected inertia and thecompliance of the hydraulic actuation system Jn²/K, which may also beviewed as a ratio of the reflected inertia to the stiffness of hydraulicactuation system, may be designed according to the following designranges. In some embodiments, the product of the reflected inertia andthe compliance of the hydraulic actuation system may be less than6.3×10⁻³ s², 1.0×10⁻³ s², 2.5×10⁻⁴ s², 6.3×10⁻⁵ s², 2.8×10⁻⁵ s²,1.6×10⁻⁵ s², or any other appropriate value. Additionally, the productof the reflected inertia and the compliance of the hydraulic actuationsystem may be greater than 1.6×10⁻⁵ s², 1.0×10⁻⁵ s², 2.5×10⁻⁶ s², or anyother appropriate value. For example, in one embodiment, the product ofthe reflected inertia and the compliance of the hydraulic actuationsystem is between about 2.5×10⁻⁶ s² and 6.3×10⁻³ s² inclusively.However, it should be understood that hydraulic actuation systemsdesigned with values both greater than and less than those noted aboveare also contemplated. Using the above design criteria, a designer mayuse the inertia of the various components in the system as well astranslation ratio and compliance of the system to provide a desiredresponse time. While any of the parameters may be varied to obtain adesired response, it is worth noting that the design parameter has alinear dependence on the inertia of the components and the compliance ofthe hydraulic actuation system and a dependence on the square of thetranslation factor. Consequently, changes in the translation factor mayprovide correspondingly larger changes in the overall response of thesystem. An example of the interplay of these parameters in designing ahydraulic actuation system are provided in more detail in the examples.

In addition to providing an appropriate response time of a hydraulicactuation system, in some embodiments, it is desirable to control thehydraulic actuation system at frequency that is similar to or greaterthan the frequency of a control event such as a body and/or wheel event.FIG. 3 shows a frequency plot relating motor torque updates 14 with bodycontrol and wheel control frequency bands associated with the typicalfrequencies of body movement 10 and wheel movement 12 of a vehicle. Fora typical passenger vehicle, body movements 10 occur between 0 Hz and 4Hz is, although higher-frequency body movement may occur well beyondthis band. Wheel movement often occurs between 8 Hz and 20 Hz, and isroughly centered around 10 Hertz. However, it should be understood thatthe body and wheel movement frequencies will differ from vehicle tovehicle and based on road conditions. A wheel event and/or body eventmay be defined as any input into the wheel or body that causes a wheeland/or body movement (including the result of a steering input). From afrequency perspective, wheel events and body events often occur atroughly 0.5 Hertz and above, see 16, and may even occur at frequenciesin excess of one thousand Hertz. Consequently, the motor input updatefrequency may vary from frequencies as low as 0.5 Hz up to, and evenpossibly greater than, 1,000 Hz, see 14. From a functional perspective,any change in a commanded motor input, such as motor torque, in responseto a wheel event and/or a body event (as measured by one or moresensors) may be considered a response to a wheel event and/or bodyevent.

In view of the above, in some embodiments, it is desirable that thehydraulic actuator be controlled at a frequency that is similar to orgreater than the frequency at which the individual body events and/orwheel events occur. Therefore, in at least one embodiment, a controlleris electrically coupled to an electric motor used to operate thehydraulic actuator, and the controller updates a motor input of theelectric motor at a rate that is faster than individual body eventsand/or wheel events. The motor input may be updated with a frequencythat is greater than about 0.5 Hz, 2 Hz, 8 Hz, 20 Hz, or any appropriatefrequency that the controller and associated electric motor are capableof being operated at. In some embodiments, the motor input may beupdated with a frequency that is less than about 1 kHz, though otherfrequencies are also possible. Therefore, in one exemplary embodiment, amotor input is controlled with a frequency between about 0.5 Hz and 1kHz inclusively.

In one exemplary embodiment, a control system commands a motor input,such as motor torque, to be updated at 10 Hz, though other frequenciesare possible. At each update, the commanded motor input is set to be thecurrent vertical body velocity (body acceleration put through a softwareintegrator) multiplied by a scaling factor k such that the actuatorcreates a force opposite to the body velocity. Such an embodiment mayimprove the body control of a vehicle. In another embodiment regardingwheel control, the commanded motor input, such as motor torque, is setto be the current actuator velocity (differential movement between thewheel and body) and multiplied by a factor k in order to counteractmovement. Here, the system responds much like a damper. It should beunderstood that the above embodiments might be used together to provideboth body control and wheel control in order to provide full vehiclecontrol. In other embodiments the commanded motor input is updated atslower rates such as 0.5 Hz or faster rates such as 1 kHz. More complexcontrol systems may also utilize other sensor data in addition to, orinstead of, body acceleration as noted previously, and may includeproportional, integral, derivative, and more complex feedback controlschemes as the disclosure is not so limited.

FIG. 4 depicts an embodiment of a hydraulic actuator 100 capable ofbeing operated in all four-quadrants of the force velocity domain as afully active actuator. A piston including a piston rod 104 and pistonhead 106 is disposed in a fluid-filled housing 102. Upon movement of thepiston, a piston head 106 forces fluid into and out of an extensionvolume 110 located on one side of the piston head and a compressionvolume 108 located on the opposing side of the piston head through oneor more concentric fluid flow tubes 122 or other appropriate connection.The fluid flow tubes 122, or other appropriate connection or portarrangement, are connected to a hydraulic motor-pump 114. Therefore, thehydraulic motor-pump 114 is in fluid communication with the compressionvolume 108 and the extension volume 110 of the hydraulic actuator asindicated by the arrows in the figure. The hydraulic motor-pump 114 isoperatively coupled to an electric motor 116 via an appropriate coupling118.

Depending on the particular embodiment, the electric motor 116 and/orthe hydraulic motor-pump 114 may either be disposed on, integrated with,or remotely located from the hydraulic actuator 100 as the disclosure isnot so limited. Alternatively, as described else where the hydraulicmotor-pump 114, electric motor 116, and the coupling 118 may beintegrated into a single smart valve capable of controlling the flow offluid between the extension volume in the compression volume ofhydraulic actuator without the need for separately operated valves.However, embodiments including separate valves are contemplated. Forexample, the fluid connections between the ports or outlets of thehydraulic motor-pump and the extension volume and compression volume ofthe hydraulic actuator may either be direct connections without anyvalves, or one or more valves may be located between the flow paths fromthe hydraulic motor-pump to the actuator as the disclosure is not solimited. Additionally, as described in more detail below, one or morevalves may also be located between the extension volume and thecompression volume of the hydraulic actuator.

It should be understood that any hydraulic motor-pump, electric motor,and coupling might be used. For example, the hydraulic motor-pump may beany device capable of functioning as a hydraulic pump or a hydraulicmotor including, for example, a gerotor, vane pump, internal or externalgear pump, gerolor, high torque/low speed gerotor motor, turbine pump,centrifugal pump, axial piston pump, or bent axis pump. In embodimentswhere the hydraulic motor-pump is a gerotor, the assembly may beconfigured so that the root and/or tip clearance can be easily adjustedso as to reduce backlash and/or leakage between the inner and outergerotor elements. However, embodiments in which a gerotor does notinclude an adjustable root and/or tip clearance are also contemplated.

In addition to the above, the electric motor 116 may be any appropriatedevice including a brushless DC motor such as a three-phase permanentmagnet synchronous motor, a brushed DC motor, an induction motor, adynamo, or any other type of device capable of converting electricityinto rotary motion and/or vice-versa. However, in some embodiments theelectric motor may be replaced by an engine-driven hydraulic motor-pump.In such an embodiment, it may be desirable to provide an electronicallycontrolled clutch or a pressure bypass in order to reduce engine loadwhile high active actuator forces are not needed. Similar to rapidlycontrolling the motor inputs of the electric motor (e.g. rapid torquechanges of the electric motor), the hydraulic motor drive (eitherthrough an electronic clutch, an electronically-controlled hydraulicbypass valve, or otherwise), may be rapidly controlled on a per wheelevent basis in order to modulate energy usage in the system.

In addition to the various types of hydraulic motor-pumps and electricmotors, the coupling 118 between the electric motor and thehydraulic-pump motor may be any appropriate coupling. For example, asimple shaft might be used, or it may include one or more devices suchas a clutch (velocity, electronically, directionally, or otherwisecontrolled) to alter the kinematic transfer characteristic of thesystem, a shock-absorbing device such as a spring pin, acushioning/damping device, a combination of the above, or any otherappropriate arrangement capable of coupling the electric motor to thehydraulic motor-pump. In some embodiments, in order to decrease responsetimes, it may be desirable to provide a relatively stiff coupling 118between the electric motor and the hydraulic motor-pump. In one suchembodiment, a short close-coupled shaft is used to connect the electricmotor to the hydraulic motor-pump. Depending on the particularembodiment, the coupling of the hydraulic motor-pump to the shaft mayalso incorporate spring pins and/or drive key features so as to reducebacklash between them.

When energy is applied to the terminals of the electric motor 116, thecoupling 118 transfers the output motion to the hydraulic motor-pump114. In some embodiments, the hydraulic motor-pump 114 and the electricmotor 116 may also be back driven. Therefore, rotation of the hydraulicmotor-pump due to an applied pressure from an associated hydraulicactuator may be transferred via the coupling 118 to rotate an outputshaft of the electric motor 116. In such an embodiment, the electricmotor may be used as a generator in which case the rotation of theelectric motor by the hydraulic motor-pump may be used to regenerateenergy. In such an embodiment, the effective impedance of the electricmotor may be controlled using any appropriate method including, forexample, pulse width modulation amongst several different loads, inorder to control the amount of energy recovered and the damping forceprovided.

In view of the above, operation of the electric motor 116 and/or thehydraulic motor-pump 114 results in movement of fluid between theextension volume and the compression volume through the hydraulicmotor-pump which results in movement of the piston rod 104 duringdifferent modes of operation. More specifically, in a first mode,rotation of the hydraulic motor-pump 114 in a first direction forcesfluid from the extension volume 110 to the compression volume 108through the one or more fluid flow tubes 122 and hydraulic motor-pump114. This flow of fluid increases a pressure of the compression volumeapplied to a first side of the piston head 106 and lowers a pressure ofthe extension volume applied to a second side of the piston head 106.This pressure differential applies a force on the piston rod 104 toextend the actuator. In a second mode, rotation of the hydraulic motor114 in a second direction such that fluid is moved from the compressionvolume 108 to the extension volume 110. Similar to the above, this flowof fluid increases a pressure of the extension volume 110 applied to thesecond side of the piston head 106 and lowers a pressure of thecompression volume 108 applied to the first side of piston head 106.This pressure differential applies a force to the piston rod 104 tocompress, or retract, the actuator. In yet another mode of operation,the hydraulic motor 114 opposes the movement of fluid between thecompression volume 108 and the extension volume 110 such that itprovides a damping force to the piston rod 104.

In view of the above, when a force generated by the pressure provided bythe hydraulic motor-pump (caused by torque from the electric motoracting on the hydraulic motor-pump), is sufficient to overcome the forceapplied to the piston rod 104, the hydraulic actuator is activelydriven. In contrast, when a force generated by pressure provided by thehydraulic motor-pump is less than a force acting on the piston rod 104,the hydraulic actuator is back driven and may be subjected to a dampingforce. Therefore, in some embodiments, the hydraulic motor-pump is apositive displacement hydraulic motor constructed and arranged to beback driven. While an embodiment including a hydraulic motor-pump andelectric motor that may be back driven is described above, embodimentsin which the hydraulic actuation system is not back drivable are alsocontemplated. In addition, in some embodiments secondary passive orelectronic valving is included in the hydraulic actuation system whichmay in certain modes decouple piston movement from electric motormovement (i.e., movement of the piston head might not create animmediate and correlated movement of the electric motor).

Since fluid volume in the fluid-filled housing 102 changes as the piston104 enters and exits the housing, the embodiment of FIG. 3 includes anaccumulator 112 to accept the piston rod volume. In one embodiment, theaccumulator 122 is a nitrogen-filled chamber with a floating piston ableto move in the housing and sealed from the hydraulic fluid. While aninternal accumulator has been depicted, any appropriate structure,device, or compressible medium capable of accommodating a change in thefluid volume present within the housing 102, including an externallylocated accumulator, might be used as the disclosure is not so limited.

The embodiment depicted in FIG. 4 may be adapted in order to accommodatea number of different fluid flow paths and should not be limited to anyparticular arrangement or method of providing fluid flow between variousportions of the housing and the hydraulic motor-pump. For example, inone embodiment, the fluid flow tubes 122 may be pipes or hydraulichoses. In another embodiment, the fluid flow tubes 122 may be theconcentric area between the inner and outer tubes of a twin-tube damperor the concentric area between each of the three tubes of a triple-tubedamper. In the above embodiments, fluid may flow in both directionsthrough the hydraulic motor-pump. In embodiments where a monotube damperarchitecture is used, a high gas pre-charge, for example, greater than35 bar, may be used to increase the hydraulic fluid stiffness and hencereduce lag and latency. In other embodiments a gas pre-charge around 25bar, or any other appropriate pressure, may be used. The hydraulicactuator may also be beneficially combined with various damper tubetechnologies including, but not limited to: McPherson strutconfigurations and damper bodies; de-aeration devices for removing airthat may be introduced during filling or otherwise without requiring adedicated air collection region inside the vibration damper; highpressure seals for a damper piston rod and/or piston head; a low costlow inertia floating piston tube (e.g. monotube); and the like.

FIG. 5 presents one embodiment of a hydraulic actuation systemintegrated into a suspension system which includes a hydraulic actuator100, hydraulic motor-pump 114, and electric motor 116 integrated into asuspension system, which may be an active suspension system. Thesuspension system is connected to a wheel 128 and located within thewheel-well of a vehicle. As depicted in the figure, the actuation systemis located where a damper is typically located and is constructed andarranged to be coupled to the suspension system between the lower 130and upper 132 suspension members. The upper and lower suspension membersmay be an upper top mount and lower control arm in a suspension systemthough other configurations are possible. As depicted in the figure, thehydraulic actuator housing 102 is connected to the lower suspensionmember 130 on one side of the hydraulic actuator and the piston, and thepiston rod 104 is connected to the upper suspension member 132 on anopposing side of the hydraulic actuator. However, it should beunderstood that the hydraulic actuator could be oriented in the oppositedirection as well. Additionally, the connections between the hydraulicactuator and the suspension members might correspond to any appropriateconnection including for example, a bushing. In some embodiments, abushing constructed to reduce noise and resonance vibrations associatedwith actuator movement might be used. Similar to the above, thehydraulic actuator 100 is also operatively connected to a hydraulicmotor-pump 114 and electric motor 116. As depicted in the figure, thehydraulic motor-pump and electric motor may be connected to, orintegrated with, the hydraulic actuator. In the depicted embodiment, thehydraulic motor-pump 114 and electric motor 116 are located between thesuspension members 130 and 132. However, embodiments in which thehydraulic motor-pump 114 and/or electric motor are remotely located fromthe hydraulic actuator 100 are also contemplated.

As illustrated in the figure, in some embodiments, a spring 124 isdisposed coaxially around the piston rod 104 and extends between theupper suspension member 132 and the hydraulic actuator body 102.Therefore, the spring will apply a force to the upper suspension member132 that is dependent on the amount of compression. In such aconfiguration, the spring 124 is located in parallel to the hydraulicactuator. However, embodiments in which the spring is located in serieswith the hydraulic actuator are also contemplated. For example, a springmight be located between the piston rod 104 and the upper suspensionmember 132 or between the hydraulic actuator housing 102 and the lowersuspension member 130. When the spring is located in series with thehydraulic actuator, a separate actuator and/or damper may be located inparallel with the spring and in series with the hydraulic actuator.

Depending on the embodiment, a hydraulic actuator may include one ormore passive and/or electronically controlled valves 126 integrated withthe hydraulic actuator housing 102, see FIG. 5. Types of valves thatmight be associated with the hydraulic actuator include, but are notlimited to, at least one of progressive valving, multi-stage valving,flexible discs, disc stacks, amplitude dependent damping valves, volumevariable chamber valving, proportional solenoid valving placed in seriesor in parallel with the hydraulic pump, electromagnetically adjustablevalves for communicating hydraulic fluid between a piston-local chamberand a compensating chamber, and pressure control with adjustable limitvalves. Additionally, a baffle plate for defining a quieting duct forreducing noise related to fluid flow might be used. A diverter valveconstructed and arranged to divert a portion of the fluid flow betweenthe compression volume and the extension volume past the hydraulicmotor-pump might also be used to limit either a pressure, flow, and/oramount of energy applied to the hydraulic motor-pump. Depending on theembodiment, the hydraulic actuator force may be at least partiallycontrolled by the one or more valves 126. Additionally the one or morevalves 126 may be pressure-operated, inertia-operated,acceleration-operated, and/or electronically controlled.

The above-noted active suspension system may also incorporate any numberof other associated components and/or alterations. For example, in oneembodiment the active suspension system is integrated with at least oneof: an inverted actuator, a telescoping actuator, an air spring, aself-pumping ride height adjustable device, and/or other appropriatedevice. Additionally, the hydraulic actuation system may include varioustypes of thermal management such as: thermal isolation between theactuator body and control/electronics; airstream cooling of electronics;and other appropriate thermal management devices and/or methods. Inanother embodiment, the hydraulic actuation system includes anappropriate connection for connecting to either a smart valve includinga hydraulic motor-pump and electric motor or to separate hydraulicmotor-pump and electric motor combination. While any appropriateconnection might be used, in one embodiment the connection correspondsto one of direct wiring, flexible cables, and/or one or more modularconnectors for connecting to a vehicle wiring harness, externallymounted power switches, and other appropriate power and/or controlsources.

As noted above, in some embodiments a hydraulic actuation system iscapable of responding on a per wheel and/or body event basis. Therefore,it is desirable that the motor input to an electric motor controllinghydraulic actuation either changes at an update rate greater than orequal to the frequency at which events occur, or that it occurs indirect response to a sensed event. FIG. 6 demonstrates a generic controlarchitecture for controlling such a hydraulic actuation system.Depending on the particular embodiment, the various components mayeither be provided separately, or one or more of them may be integratedor attached together as the disclosure is not so limited. In thedepicted embodiment, the hydraulic actuation system includes anelectronic controller 200. In some embodiments, the controller is acorner controller configured to control an active suspension systemassociated with a single wheel. As depicted in the figure, thecontroller is electrically coupled to an electric motor 116, which is athree-phase electric motor with an encoder in the current embodiment.One possible electrical topology of such an embodiment includes athree-phase bridge, with six MOSFET transistors where each motor phaseis connected to the junction between two MOSFETs in series. In such anembodiment, the high side MOSFET is connected to the voltage rail andthe low side MOSFET is connected to ground and the controller rapidlypulse-width-modulates a control signal to the gate of each MOSFET inorder to drive the motor for 116. However, other types of electricmotors and control methods might also be used including, for example, asensorless control instead of an encoder.

The controller 200 is configured to receive signals from one or moreinputs 202 corresponding to various different information sources inorder to determine how to control a motor input of the electric motor200 and thus the hydraulic actuator. These sensors may provideinformation related to sensing individual wheel events, body events,and/or other pertinent information. The controller 200 may receiveinputs from sensors that are external to the hydraulic actuator or fromsensors that are integrated with, or disposed on, the hydraulicactuator. Sensors located external to the hydraulic actuator may eitherbe sensors dedicated to the hydraulic actuator, or they may be sensorsintegrated with the vehicle body as the disclosure is not so limited.The above noted sensors correspond to one or more of the followingsensor architectures: wheel acceleration sensing; body accelerationsensing, fluid pressure sensing; position sensing; smart valve localsensing; motor position sensing; multi-sensor whole vehicle sensing;centralized inertial measurement unit sensor architecture; the vehicleCAN bus, one or more sensors associated with a wheel (e.g.accelerometers), and one or more sensors associated with an axle (e.g.accelerometers). In another embodiment, the input received by thecontroller 200 is a signal from a central controller associated with oneor more other controllers and hydraulic actuators and may provideinformation related to other body events, wheel events, or otherrelevant information sensed by the other controllers, or input to thecentral controller.

In one particular embodiment, the inputs received by the controller 200include information from a rotor position sensor that senses theposition and/or velocity of the electric motor. This sensor may beoperatively coupled to the electric motor directly or indirectly. Forexample, motor position may be sensed without contact using a magneticor optical encoder. In another embodiment, rotor position may bemeasured by measuring the hydraulic pump position, which may berelatively fixed with respect to the electric motor position. This rotorposition or velocity information may be used by a controller connectedto the electric motor. The position information may be used for avariety of purposes such as: motor commutation (e.g. in a brushless DCmotor); actuator velocity estimation (which may be a function of rotorvelocity for systems with a substantially positive displacement pump);electronic cancellation of pressure fluctuations and ripples; andactuator position estimation (by integrating velocity, and potentiallycoupling the sensor with an absolute position indicator such as amagnetic switch somewhere in the actuator stroke travel such thatactivation of the switch implies the actuator position is in a specificlocation). Without wishing to be bound by theory, by coupling an activesuspension containing an electric motor and/or hydraulic pump with arotary position sensor coupled to it, the system may be more accuratelyand efficiently controlled.

Other possible embodiments of inputs 202 include information such asglobal positioning system (GPS) data, self-driving parameters, vehiclemode setting (i.e. comfort/sport/eco), driver behavior (e.g. howaggressive is the throttle and steering input), body sensors(accelerometers, inertial measurement units, gyroscopes from otherdevices on the vehicle), safety system status (e.g. ABS braking engaged,electronic stability program status, torque vectoring, airbagdeployment), and other appropriate inputs. For example, in oneembodiment, a suspension system may interface with GPS on board thevehicle and the vehicle may include (either locally or via a networkconnection) a map correlating GPS location with road conditions. In thisembodiment, the active suspension may control hydraulic actuation systemwithin the suspension to react in an anticipatory fashion to adjust thesuspension in response to the location of the vehicle. For example, ifthe location of a speed bump is known, the actuators can start to liftthe wheels immediately before impact. Similarly, topographical featuressuch as hills can be better recognized and the system can respondaccordingly. Since civilian GPS is limited in its resolution andaccuracy, GPS data can be combined with other vehicle sensors such as aninertial measurement unit (or accelerometers) using a filter such as aKalman Filter in order to provide a more accurate position estimateand/or any other appropriate device.

By integrating an active suspension with other sensors and systems onthe vehicle, the ride dynamics may be improved by utilizing predictiveand reactive sensor data from a number of sources (including redundantsources, which may be combined and used to provide greater accuracy tothe overall system). In addition, the active suspension may sendcommands to other systems such as safety systems in order to improvetheir performance. Several data networks exist to communicate this databetween subsystems such as CAN (controller area network) and FlexRay.

While several types of sensors and control arrangements are noted above,it should be understood that other appropriate types of inputs, sensors,and control schemes are also contemplated as the disclosure is not solimited. The inputs 202 indicated in FIG. 6 may also include informationderived from the electric motor including, for example, calculatingactuator velocity by measuring electric motor velocity as well ascalculating actuator force by measuring electric motor current to name afew. In other embodiments, the inputs 202 include information fromlook-ahead sensors, such as controllers associated with actuators on therear axle of a vehicle receiving information from the front wheels toadjust control of the hydraulic actuator before an event occurs.

In the system-level embodiment of FIG. 6, energy flows into and out ofthe controller on the suspension electrical bus 204. The suspensionelectrical bus 204 may be direct current, though embodiments usingalternating current are also contemplated. While not shown in FIG. 6, inone embodiment multiple actuators 100 and controllers 200 share a commonsuspension electrical bus 204. In this way, if one actuator and/orcontroller pair is regenerating energy, another pair can be consumingthis regenerated energy. In some embodiments the voltage of thesuspension electrical bus 204 is held at a voltage V_(high) higher thanthat of the vehicle's electrical system, such as 48 volts, 380 volts, orany other appropriate voltage. Without wishing to be bound by theory,such an embodiment may enable the use of smaller wires with lowercurrents providing a potential cost, weight, and integration advantage.In other embodiments this voltage is substantially similar to thevehicle's electrical system voltage (12, 24 or 48 volts), which mayeliminate or reduce the need for a DC-DC converter 206. However, in someembodiments it may be desirable to use a voltage V_(low) lower than thevehicle's electrical system to reduce the need for a super capacitor,

In the embodiment of FIG. 6, the suspension electrical bus 204interfaces with the vehicle's electrical system 210 and the vehicle'senergy storage 212, for example, the main battery, or other appropriateenergy storage, through a bidirectional DC-DC converter 206. Appropriatebidirectional converters include both galvanically isolated andnon-galvanically isolated converters. However, other devices capable ofconverting the electrical signal between the suspension electrical bus204 and the vehicle's electrical system 210 might be used. A fewpossible topologies include a synchronous buck converter (where thefreewheeling diode is replaced with a transistor), a transformer withfast-switching DC/AC converters on each side, and resonant converters,and other appropriate devices.

Modern vehicles are typically limited in their capacity to acceptregenerative electrical energy from onboard devices, and to deliverlarge amounts of energy to onboard devices. Without wishing to be boundby theory, in the former, regenerated energy may cause a vehicle'selectrical system voltage to rise higher than allowable, and in thelatter, large power draws may cause a voltage brownout, or under-voltagecondition for the vehicle. In order to deliver sufficient power to anactive suspension, or to capture a maximal amount of regenerated energy,a form of energy storage associated with the suspension system itselfmay be used. Energy storage may be in the form of batteries such aslithium ion batteries with a charge controller, ultra-capacitors, orother forms of electrical energy storage. In the embodiment of FIG. 6,the negative terminal of one or more ultra-capacitors 208 are connectedto a positive terminal of a vehicle electrical system 212, and thepositive terminal is connected to the suspension electrical bus 204running at a voltage higher than the vehicle electrical system voltage.In such an embodiment, the ultra-capacitor, or other appropriate storagedevice located on the part bus, may be sized to accommodate regenerativeand/or expected consumption spikes, in order to effectively controlwheel movement and regenerate energy during damping (bidirectionalenergy flow) and limit the impact of such a suspension system on theoverall vehicle electrical system. However, as noted above, otherembodiments are also possible including, for example, the energy storagemay be placed directly on the suspension electrical bus or the vehicleelectrical system.

Due to the ability to store regenerated energy locally on the supercapacitor 208 or other appropriate device, as well as the vehicle energystorage device 212, the above described embodiments may be eitherself-powered or at least partially self-powered by the regeneratedenergy. Several advantages may be achieved by combining an activesuspension with a self-powered architecture. An active suspension may befailure tolerant of a power bus failure, wherein the system can stillprovide damping, even controlled damping with a bus failure. Anotheradvantage is the potential for a retrofittable semi-active or fullyactive suspension that may be installed OEM or aftermarket on vehiclesand not require any wires or power connections. Such a system maycommunicate with each actuator device wirelessly or through hardconnections such as the vehicle CAN. Energy to power the system may beobtained through recuperating dissipated energy from damping. This hasthe advantage of being easy to install and lower cost. Another advantageis that such a system may function as an energy efficient activesuspension. More specifically, by utilizing the regenerated energy inthe active suspension, DC/DC converter losses can be minimized such thatrecuperated energy is not delivered back to the vehicle, but rather,stored and then used directly in the suspension at a later time. Thoughas noted above, embodiments in which energy is delivered back to thevehicle are also contemplated.

While in some embodiments a hydraulic actuation system incorporated intoa suspension system may be a net consumer or producer of energy, inother embodiments, it may be desirable to provide a hydraulic actuationsystem that is substantially energy neutral during use to provide anenergy efficient suspension system. In such an embodiment, a controllerassociated with a hydraulic actuation system controls the motor inputsassociated with the electric motor in response to road conditions, wheelevents, and/or body events such that the energy harvested duringregenerative cycles (e.g. during damping) and the energy concernedduring active cycles of the suspension system (on-demand energydelivery) are substantially equal over a desired time period. As notedpreviously, the regenerated energy intended for subsequent usage may bestored in any appropriate manner including local energy storageassociated with individual hydraulic actuators, or energy might bestored at the vehicle level. Appropriate types of energy storageinclude, but are not limited to, super capacitors, batteries, flywheels,hydraulic accumulators, or any other appropriate mechanism capable ofstoring the recaptured kinetic energy and subsequently providing it foruse by the system for reconversion into kinetic energy in a desiredamount and at a desired time.

Referring to the embodiment of FIG. 6, in some embodiments using aneutral energy control, the controller 200 may control the energy flowsuch that energy captured via regeneration from small amplitude and/orlow frequency wheel and/or body events is stored in the super capacitor208. Once the super capacitor is fully charged, additional regeneratedenergy is either transferred to the vehicle electrical bus 210 to eithercharge the vehicle energy storage device 212, be consumed by loadsconnected to the vehicle electrical bus 210, and/or dissipated as heaton a dissipative resistor. When the suspension control system requiresenergy, such as to resist movement of a wheel or to encourage movementof a wheel in response to a sensed event, energy is drawn from the supercapacitor 208 and/or from the vehicle electrical bus 210 via thebidirectional power converter 206. Energy that is consumed to managevarious sensed events is replaced during subsequent regenerative eventsas described above. When the relative amounts of regeneration and activeactuation are appropriately controlled, the controller provides asubstantially energy neutral suspension control over a desired timeperiod. In other embodiments, the controller controls the relativeamounts of regeneration over a desired time period to provide an averagepower with a magnitude that is less than or equal to 75 watts, 50 watts,or any other desired average power. This average power may either bepositive corresponding to energy consumption, and/or negativecorresponding to energy regeneration. Such a control system is notlimited to a fully active system including regenerative and practicecontrol. Instead, limiting an average power of the system may also beapplied to purely active systems and purely regenerative systems such asmight be seen in a hydraulic actuation system and/or a semi-activesuspension system.

FIG. 7 illustrates an exemplary implementation of energy neutral controlof a suspension system. The figure shows power flow 300 over time.Positive y-axis values 302 correspond to regenerated energy duringdamping and negative y-axis values 304 correspond to energy consumedduring active actuation. In the depicted embodiment, a controllerregulates the force of a full active suspension and the resulting powerflow curve 300 such that average power is within a window 306substantially close to zero such as, for example, 75 W or 50 W ofregeneration and/or consumption over an extended period of time. Such acontrol system may be considered an energy neutral control system.

The control system of an active suspension system such as that shown inFIG. 4 may involve a variety of parameters such as wheel and bodyacceleration, steering input, braking input, and look-ahead sensors suchas vision cameras, planar laser scanners, and the like. In oneembodiment of an energy neutral control system, the controllercalculates a running average of power (consumed or regenerated) thoughembodiments in which the power is tracked from ignition might also beused. In one embodiment, the average powers calculated by taking thetotal power equal to the integral of the power flow curve 300 over thedesired time period and dividing it by the time period. The controllermay then alter a gain parameter in a control algorithm to bias controlof the suspension system more towards either the regenerative region ifexcess power consumption has occurred or the active actuation region ifexcess power regeneration has occurred in order to keep the averagepower within the neutral band 306, which may also be referred to as anactive control demand threshold. For example, during an extended highlateral acceleration turn, a control algorithm may slowly allow thevehicle to roll, thus reducing the instantaneous power consumption, andover time will reduce the energy consumed (a lower average power). Whilein energy neutral system has been described above with regards to anelectrical system, embodiments of a control system implementing anactive control demand threshold with a mechanical system are alsocontemplated. For example, hydraulic energy may be dissipated using anappropriate element and/or captured using a hydraulic accumulator. Onesuch embodiment that may be controlled in such a manner as describedabove involving the use of two electronically controlled valves andthree check valves.

While embodiments described above are directed to providing an averagepower flow of a single hydraulic actuator that is energy neutral, thedisclosure is not so limited. Instead, in some embodiments an averagepower flow may be taken as the sum of all the hydraulic actuatorslocated within a vehicle or other system. Additionally, the averagepower flow might be determined for a subset of the hydraulic actuatorslocated within the vehicle or system. The average may also be over alltime, between vehicle ignition starts, over a small time window, or overany other appropriate time period.

In some situations, it may be desirable to override the energy neutrallimits described above. For example, during a safety mode associatedwith sensing events such as avoidance, braking, fast steering, and/orother safety-critical maneuver, the power limits associated with theenergy neutral system are overridden. One embodiment of a safetymaneuver detection algorithm is a trigger if the brake position isdepressed beyond a certain threshold, and the derivative of the position(i.e. the brake depression velocity) also exceeds a threshold. Otherembodiments of a safety maneuver detection algorithm include the use oflongitudinal acceleration thresholds, steering thresholds, and/or otherappropriate inputs. In one specific embodiment, a fast control loopcompares a threshold emergency steering threshold to a factor derived bymultiplying the steering rate and a value from a lookup table indexed bythe current speed of the vehicle. The lookup table may contain scalarvalues that relate maximum regular driving steering rate at each vehiclespeed. For example, in a parking lot a quick turn is a conventionalmaneuver. However, at highway speeds the same quick turn input is likelya safety maneuver where the suspension should disregard energy limits inorder to keep the vehicle stabilized. In another exemplary embodiment, avehicle rollover model for SUVs may be utilized that incorporates anumber of sensors such as lateral acceleration to change the suspensiondynamics if an imminent rollover condition is detected. In manyreal-world applications, a number of these heuristics (braking,steering, lane-departure/traffic detection sensors, deceleration,lateral acceleration, etc.) may be fused together (such as by usingfuzzy logic) to come to a desired control determination in order tocontrol the suspension system. Depending on the embodiment, the controldetermination might not be binary, but rather may be a scaling factor onthe power limits.

In another embodiment, a controller of suspension system adjusts how itresponds to sensed wheel and/or body events based on the availability ofenergy reserves within the energy storage, such as a super capacitor,present within the hydraulic actuation system. More specifically, asenergy reserves begin to diminish, responses to some wheel events mighttransition from consuming energy to harvesting energy from the actuatormovements. In an example of self-powered adaptive suspension control,energy captured via regeneration from small amplitude and/or lowfrequency wheel events may be stored in the super capacitor of FIG. 6.When the suspension control system requires energy, such as to resistmovement of a wheel at very low velocities substantially close to zerovelocity, or to actively move a wheel, in response to a wheel event,energy may be drawn from the super capacitor. As energy reserves in thesuper capacitor, or other appropriate device, are diminished, thecontroller biases the system responses towards regeneration and energyconservation until the energy reserves are sufficiently replenished toresume “normal” active suspension operation.

Combining a suspension capable of adjusting its power consumption overtime using energy optimizing algorithms and/or energy neutral algorithmsmay enhance the efficiency of the suspension. In addition, it may allowan active suspension to be integrated into a vehicle withoutcompromising the current capacity of the alternator. For example, thesuspension may adjust to reduce its instantaneous energy consumed inorder to provide enough vehicle energy for other subsystems such as ananti-lock braking system (ABS brakes), electric power steering, dynamicstability control, and engine control units (ECUs).

In another exemplary embodiment, a suspension system as described hereinmay be associated with an active chassis power management system adaptedto control power throttling of the suspension system. More specifically,a controller responsible for commanding the active suspension respondsto energy needs of other devices on the vehicle such as active rollstabilization, electric power steering, other appropriate devices,and/or energy availability information such as alternator status,battery voltage, and/or engine RPM. Further, when needed the controllermay reduce the power consumption of the suspension system when power isrequired by other devices and/or when there is low system energy asindicated by the alternator status, battery voltage, and/or engine RPM.For example, in one embodiment, a controller of a suspension reduces itsinstantaneous and/or time-averaged power consumption if one of thefollowing events occur: vehicle battery voltage drops below a certainthreshold; alternator current output is low, engine RPM is low, thebattery voltage is dropping at a rate that exceeds a preset threshold; acontroller (e.g. an engine control unit) on the vehicle commands a powerconsumer device (such as electric power steering) at a relatively highpower (for example, during a sharp turn at low speed); an economy modesetting for the active suspension is activated, and/or any otherappropriate condition where a reduced power consumption would be desiredoccurs.

In addition to neutral energy control, FIG. 7 also provides an exampleof on-demand energy delivery for an active suspension system. When anon-demand energy delivery-capable active suspension system experiencespositive energy flow 302 (when the graph is above the center line), anelectric motor, or other appropriate associated device, capable ofacting as a generator may utilize this energy to generate electricity.This may occur when fluid flows past the hydraulic motor 114 in FIG. 4due to wheel rebound action or compression. This flow of fluid is usedto turn the electric generator, thereby producing electricity that maybe stored for on-demand consumption, or it may be instantaneouslyconsumed by another associated device within a vehicle or anothersuspension system including a hydraulic actuator. In contrast toregeneration, when an on-demand energy delivery capable suspensionsystem experiences negative energy flow 304 (when the graph is below thecenter line), energy is being consumed as needed (e.g. on-demand). Theconsumed energy may either be used to actively actuate the hydraulicactuator in a desired direction, or it may be used applied as a counteracting current into the generator, thereby resisting the rotation of thehydraulic motor which in turn increases pressure in the actuator causingthe wheel movement driving the demand to be mitigated. The consumedpower may correspond to energy harvested during a previous regenerationcycle. Alternatively, the energy can be consumed from a variety ofdifferent sources including, for example, energy storage devicesassociated with the suspension system, a vehicle's 12V or 48V electricalsystem, and/or any other applicable energy storage system capable ofdelivering the desired power flow to and from the suspension system.

In one example of a suspension system and controlled to provideon-demand energy, energy consumption might be required throughout awheel event, such as when a vehicle encounters a speed bump. Energy maybe required to lift the wheel as it goes over a speed bump (that is,reduce distance between the wheel and vehicle) and then push the wheeldown as it comes off of the speed bump to keep the vehicle more levelthroughout. However, rebound action, such as the wheel returning to theroad surface as it comes down off of the speed bump may, fall into thepositive energy flow cycle by harnessing the potential energy in thespring, using extension damping to regenerate energy.

While embodiments directed to suspension systems capable of bothregeneration and active actuation are described above, embodiments ofsuspension systems that do not regenerate power, and/or dissipateregenerated power are also contemplated.

FIG. 13 shows an embodiment of a suspension actuator that includes asmart valve. The active suspension actuator 602 includes an actuatorbody (housing) 604 and a smart valve 606. The smart valve 606 is closecoupled to the actuator body 604 so that there is a tight integrationand short fluid communication between the smart valve and the fluidbody, and is sealed so that the integrated active suspension smart valveassembly becomes a single body (or housing) active suspension actuator.In the embodiment shown in FIG. 13 the smart valve 606 is coupled to theactuator body 604 so that the axis of the smart valve (i.e. therotational axis of the integrated hydraulic motor-pump and electricmotor) 630 is parallel with the axis of actuator body 632. It should beunderstood that while a close coupled connection with an actuator bodyhas been depicted, embodiments in which the smart valve is integratedinto the same housing as the actuator body, connected to the actuatorthrough the use of hoses or other similar mechanisms, as well as otherconnection arrangements are also contemplated.

The integrated smart valve 606 includes an electronic controller 608, anelectric motor 610 that is close coupled to hydraulic motor (e.g. anHSU) 612. The hydraulic motor-pump has a first port 614 that is in fluidcommunication with a first chamber 616 in the actuator body 604 and asecond port 618 that is in fluid communication with a second chamber 620in the actuator body 604. The first port and second port include ahydraulic connection constructed and arranged to place the smart valvein fluid communication with the actuator In one embodiment, thehydraulic connection includes a first tube inside a second tube. Thefirst port corresponds to the first tube, and the second portcorresponds to the annular area between the first tube and second tube.In an alternate embodiment the hydraulic connection may simplycorrespond to two adjacent ports. Hydraulic seals may be used to containthe fluid within the first and second hydraulic connections as well asto ensure that fluid is sealed within the actuator. It should beunderstood that many other permutations of hydraulic connectionarrangements can be constructed and the disclosure is not limited toonly the connection arrangements described herein.

In the embodiment disclosed in FIG. 13 the first chamber is an extensionvolume and the second chamber is a compression volume, however, thesechambers and volumes may be transposed and the disclosure is not limitedin this regard. The hydraulic motor-pump 612 is in hydrauliccommunication with the first and second chambers located on opposingsides of a piston 622 which is connected to a piston rod 624. Therefore,when the piston and piston rod move in a first direction (i.e. anextension stroke) the hydraulic motor-pump rotates in a first direction,and when the piston and piston rod move in a second direction (i.e. acompression stroke) the hydraulic motor rotates in a second rotation.The close coupling of the hydraulic motor-pump through the first andsecond ports with the extension and compression chambers of the actuatormay allow for a very stiff hydraulic system which may desirably improvethe responsiveness of the actuator. As described previously, a fastresponse time for the actuator system is highly desirable, especiallyfor active suspension systems where it may need to respond to wheelevents acting at 20 Hz and above. As detailed previously, the responsetime of a second order system is directly proportional to its naturalfrequency and the system depicted in FIG. 13, has a natural frequency ofabout 30 Hz (resulting in a response time of less than 10 ms). In viewof the above, similar systems should be able to readily provide naturalfrequencies anywhere in the range of about 2 Hz to 100 Hz though otherfrequencies are also possible.

The active suspension actuator 602 may have a high motion ratio from thelinear speed of the piston 622 and piston rod 624 to the rotationalspeed of the close coupled hydraulic motor-pump and electric motor.Therefore, during high velocity suspension events, extremely highrotational speeds may be achieved by the close coupled hydraulicmotor-pump and electric motor. This may cause damage to the hydraulicmotor-pump and electric motor. To overcome this issue and allow theactuator to survive high speed suspension events, in some embodiments,passive valving may be incorporated to act hydraulically in eitherparallel, in series, or a combination of both with the hydraulicmotor-pump. Such passive valving may include a diverter valve(s) 626.The diverter valve(s) 626 is configured to activate at a preset fluidflow rate (i.e. a fluid diversion threshold) and will divert hydraulicfluid away from the hydraulic motor-pump 612 in response to thehydraulic fluid flowing at a rate that exceeds the fluid diversionthreshold. The fluid diversion threshold may be selected so that themaximum safe operating speed of the hydraulic motor-pump and motor isnever exceeded, even at very high speed suspension events. When thediverter activates and enters the diverted flow mode, restricting fluidflow to the hydraulic motor-pump, a controlled split flow path iscreated so that fluid flow can by-pass the hydraulic pump in acontrolled manner, thereby creating a damping force on the actuator sothat wheel damping is achieved when the diverter valve is in thediverted flow mode. A diverter valve may be incorporated in at least oneof the compression and extension stroke directions. The divertervalve(s) may be located in the extension volume and compression volumeas shown in the embodiment of FIG. 13 or elsewhere in the hydraulicconnection between the actuator body 604 and the hydraulic motor-pump612 as the disclosure is not limited in this regard. Other forms ofpassive valving may also be incorporated to act hydraulically in eitherparallel, in series, or a combination of both, with the hydraulicmotor-pump. For example, a blow-off valve(s) 628 might be used. The blowoff valve(s) can be adapted so that they can operate when a specificpressure drop across the piston 622 is achieved, thereby limiting themaximum pressure in the system. The blow off valve(s) 628 may be locatedin the piston as shown in the embodiment of FIG. 13 or elsewhere in thehydraulic connection between the actuator body 604 and the hydraulicmotor-pump 612.

The passive valving used with the active suspension actuator 602 can beadapted so as to provide a progressive actuation, thereby minimizing anynoise vibration and harshness (NVH) induced by their operation. Thepassive valving that may be incorporated in the active suspensionactuator may comprise at least one of progressive valving, multi-stagevalving, flexible discs, disc stacks, amplitude dependent dampingvalves, volume variable chamber valving, and a baffle plate for defininga quieting duct for reducing noise related to fluid flow. Other forms ofcontrolled valving may also be incorporated in the active suspensionactuator, such as proportional solenoid valving placed in series or inparallel with the hydraulic motor-pump, electromagnetically adjustablevalves for communicating hydraulic fluid between a piston-local chamberand a compensating chamber, and pressure control with adjustable limitvalving. While particular arrangements and constructions of passive andcontrolled valving are disclosed above, other arrangements andconstructions are also contemplated.

Since fluid volume in the actuator body 604 changes as the piston 624enters and exits the actuator, the embodiment of FIG. 13 includes anaccumulator 634 to accept the piston rod volume. In one embodiment, theaccumulator is a nitrogen-filled chamber with a floating piston 636 ableto move in the actuator body and sealed from the hydraulic fluid with aseal 638. In the depicted embodiment, the accumulator is in fluidcommunication with the compression chamber 616. The nitrogen in theaccumulator is at a pre-charge pressure, the value of which isdetermined so that it is at a higher value than the maximum workingpressure in the compression chamber. The floating piston 636 rides inthe bore of an accumulator body 640 that is rigidly connected to theactuator body 604. A small annular gap 642 exists between the outside ofthe accumulator body 640 and the actuator body 604 that is in fluidcommunication with the compression chamber, and hence is at the samepressure (or near same pressure) as the accumulator, thereby negating orreducing the pressure drop between the inside and outside of theaccumulator body. This arrangement allows for the use a thin wallaccumulator body, without the body dilating under pressure from thepre-charged nitrogen.

While an internal accumulator has been depicted, any appropriatestructure, device, or compressible medium capable of accommodating achange in the fluid volume present within the actuator 604, including anexternally located accumulator, might be used, and while the accumulatoris depicted as being in fluid communication with the compressionchamber, the accumulator could be in fluid communication with theextension chamber, as the disclosure is not so limited.

The compact nature and size of the integrated smart valve and activesuspension actuator of the embodiment of FIG. 13 occupies a volume andshape compatible with vehicle suspension damper wheel well clearances.This may enable easy integration into a vehicle wheel well. The smartvalve occupies a suitable volume and shape such that during full rangeof motion and articulation of the active suspension actuator, apredetermined minimum clearance is maintained between the smart valveand all surrounding components of a conventional vehicle wheel well. Thesize of the smart valve as disclosed in FIG. 13 is less than 8″ (203 mm)in diameter and is less than 8″ (203 mm) in length. However, othersizes, dimensions, and orientations are also possible.

FIG. 14 shows one embodiment of a smart valve 702. As disclosed in theembodiment of FIG. 13, a fluid filled housing 704 is coupled with thecontrol housing 706. The control housing is integrated with the smartvalve 702. The smart valve assembly includes a hydraulic motor-pumpassembly (HSU) 708 closely coupled and operatively connected to a rotor710 of an electric motor/generator. The stator 712 of the electricmotor/generator is rigidly located to the body of the electro-hydraulicvalve assembly 702. The hydraulic motor-pump includes a first port 714that is in fluid communication with a first chamber of the actuator anda second port 716 that is in fluid communication with a second chamberof the actuator. The second port 716 is also in fluid communication withfluid 718 that is contained within the volume of the housing 704. Thehydraulic motor-pump and electric motor/generator assembly is containedwithin and operates within the fluid 718 contained in the fluid filledhousing 704.

For reasons of reliability and durability the electric motor/generatormay a brushless DC motor and electric commutation may be carried out viathe electronic controller and control protocols, as opposed to usingmechanical means for commutation (such as brushes for example), whichmay not remain reliable in an oil filled environment. However,embodiments using brush motors and other types of motors are alsocontemplated. As the fluid 718 is in fluid communication with the secondport 716 of the hydraulic motor-pump 708, any pressure that is presentat the second port of the hydraulic motor-pump will also be present inthe fluid 718. The fluid pressure at the second port may be generated bythe pressure drop that exists across the hydraulic motor-pump (and henceacross the piston of the actuator of the embodiment of FIG. 13) and maychange accordingly with the pressure drop (and hence force) across thepiston. The pressure at the second port may also be present due to apre-charge pressure that may exist due to a pressurized reservoir (thatmay exist to account for the rod volume that is introduced or removedfrom the working volume of the actuator as the piston and piston rodstrokes, for example). This pre-charge pressure may fluctuate withstroke position, with temperature or with a combination of both. Thepressure at the second port may also be generated as a combination ofthe pressure drop across the hydraulic motor-pump and the pre-chargepressure.

The control housing 706 is integrated with the smart valve body 702 andcontains a controller cavity 720. The controller cavity 720 is separatedfrom the hydraulic fluid 718 that is contained within the housing 704 bya bulkhead 722, or other pressure sealed barrier. The pressure withincontroller cavity 720 is at atmospheric (or near atmospheric) pressure.The bulkhead 722 contains the fluid 718 within the fluid-filled housing704, by a seal(s) 724, acting as a pressure barrier between the fluidfilled housing and the control cavity. The control housing 706 containsa controller assembly 726 which may be an electronic controller assemblyincluding a logic board 728, a power board 730, and a capacitor 732among other components. In some embodiments, the controller assembly isrigidly connected to the control housing 706. The electricmotor/generator stator 712 includes winding electrical terminations 734that are electrically connected to a flexible electrical connection(such as a flex PCB for example) 736 that is in electrical communicationwith an electronic connector 738. The electronic connector 738 passesthrough the bulkhead 722 while still isolating the controller cavityfrom the fluid filled portion of the housing through the use of a sealedpass-through 740.

Since the bulkhead 722 contains the fluid 718 within the fluid filledhousing 704, the bulkhead is subjected to the pressure variations of thefluid 718 due to the pressure from the second port 716 of the hydraulicmotor-pump. On the opposing side of the bulk head the bulkhead issubjected to atmospheric (or near atmospheric) pressure. This may createa pressure differential across the bulkhead which may cause the bulkheadto deflect. Even if the bulkhead is constructed from a strong and stiffmaterial (such as steel for example), any change in the pressuredifferential between the fluid 718 and the controller cavity 720 maycause a change in the deflection of the bulkhead. As the sealedpass-through 740 passes through the bulkhead, any change in deflectionof the bulkhead may impart a motion to the sealed pass-through, whichmay in turn impart a motion to the electronic connector 738 that iscontained within the sealed pass-through. The flexible electricalconnection 736 is adapted so that it can absorb, or otherwiseaccommodate, motions between the electrical connector 738 and thewinding electrical terminations 734. Therefore, the connections betweenthe winding electrical terminations 734 and the flexible electricalconnection 736 and between the flexible electrical connection 736 andthe electronic connector 738 may be protected from fatigue which couldlead to failure.

The electrical connector 738 may be in electrical communication with thepower board 730 via another compliant electrical member (not shown). Thecompliant electrical member is adapted so that it can absorb any motionsthat may exist between the electrical connector 738 and the power board730 so that the connections between the power board 730 and thecompliant electrical member and between compliant electrical member 742and the electronic connector 738 do not become fatigued over time whichmay cause these connections to fail as well.

The control housing 706 contains the control assembly 726 which mayinclude a logic board, a power board, capacitors and other electroniccomponents such as FETs or IGBTs. To offer an efficient means of heatdissipation for the control assembly 726, the control housing 706 mayact as a heat sink, and may be constructed from a material that offersgood thermal conductivity and mass (such as an aluminum or heatdissipating plastic for example). To ensure that an efficient heatdissipating capability is achieved by the control housing 706, the powercomponents of the control assembly 726 (such as the FETs or IGBTs) maybe mounted flat and in close contact with the inside surface of thecontrol housing 706 so that it may utilize this surface as a heat sink.The construction of the control housing 706 may be such that the heatsink surface may be thermally isolated from the fluid filled housing704, by constructing the housing from various materials and usingmethods such as overmolding the heat sink surface material with athermally nonconductive plastic that is in contact with the housing 704.Alternatively, the control housing 706 may be constructed so that theheat sink surface is thermally connected to the fluid filled housing704. As a smart valve may be disposed in a wheel well of a vehicle, theheat sink feature of the control housing 706 may be adapted andoptimized to use any ambient air flow that exists in the wheel well tocool the thermal mass of the heat sink.

In some embodiments, a rotary position sensor 742, that measures therotational position of a source magnet 744 that is drivingly connectedto the electric motor/generator rotor 710, is mounted directly to thelogic board 728. The rotary position sensor may be of a Hall effect typeor other type. A non-magnetic sensor shield 746 is located within thebulkhead and lies in between the source magnet 744 and the rotaryposition sensor 742. Consequently, the sensor shield contains the fluid718 that is in the fluid filled housing while allowing the magnetic fluxof the source magnet 744 to pass through unimpeded so that it can bedetected by the rotary position sensor 742 in order to detect theangular position of the rotor 710.

The signal from the rotary position sensor 742 may be used by theelectronic controller for commutation of the BLDC motor as well as forother functions such as for the use in a hydraulic ripple cancellationalgorithm (or protocol). Without wishing to be bound by theory, allpositive displacement hydraulic pumps and motors (e.g. HSUs) produce apressure pulsation that is in relation to its rotational position. Thispressure pulsation is generated because the hydraulic motor-pump doesnot supply an even flow per revolution. Instead, the hydraulicmotor-pump produces a flow pulsation per revolution, whereby at certainpositions the hydraulic motor-pump delivers more flow than its nominaltheoretical flow per revolution (i.e. an additional flow), and at otherposition the hydraulic motor-pump delivers less flow than its nominaltheoretical flow per revolution (i.e. a negative flow). The profile ofthe flow pulsation (or ripple) is known with respect to the rotaryposition of the hydraulic motor-pump. This flow ripple then in turngenerates a pressure ripple in the system due to the inertia of therotational components and the mass of the fluid etc. and this pressurepulsation can produce undesirable noise and force pulsations indownstream actuators etc. Since the profile of the pressure pulsationcan be determined relative to the pump position, which may be measuredfrom the rotor position using the source magnet position, it is possiblefor the controller to use a protocol that can vary the motor current andhence the motor torque based upon the rotor position signal tocounteract these pressure pulsations. This may help to mitigate orreduce the pressure pulsations and hence reduce the hydraulic noise andimprove the performance of the system. Another method of reducinghydraulic ripple from the hydraulic motor-pump may be in the use of aport timed accumulator buffer. In this arrangement the hydraulicmotor-pump contains ports that are timed in accordance with thehydraulic motor-pump flow ripple signature so that in positions when thehydraulic motor-pump delivers more flow than its nominal (i.e. anadditional flow) a port is opened from the hydraulic motor-pump firstport to a chamber that contains a compressible medium so that there isfluid flow from the hydraulic motor-pump to the chamber to accommodatethis additional flow, and at positions when the hydraulic motor-pumpdelivers less flow than its nominal (i.e. a negative flow) a port isopened from the hydraulic motor-pump first port to the reservoir thatcontains a compressible medium so that the fluid can flow from thereservoir to the hydraulic motor-pump first port, to make up for thenegative flow. The chamber with the compressible medium thereby buffersout the flow pulsations and hence the pressure pulsations from thehydraulic motor-pump. It is possible to use the hydraulic ripplecancellation algorithm described earlier with the port timed accumulatorbuffer described above to further reduce the pressure ripple and noisesignature of the hydraulic motor-pump thereby further improving theperformance of the smart valve.

FIG. 15 which shows an embodiment of a suspension system 802 includingan actuator body (housing) 804 and a smart valve 806. The smart valve806 is close coupled to the actuator body 804 so that there is a tightintegration and short fluid communication between the smart valve andthe fluid body, and is sealed so that the integrated active suspensionsmart valve assembly either is, or may function as, a single body (orhousing) suspension system. The integrated smart valve 806 includes anelectronic controller 808 and an electric motor 810 that is closecoupled to a hydraulic motor-pump (e.g. an HSU) 812. The hydraulicmotor-pump has a first port 814 that is in fluid communication with afirst chamber 816 in the actuator body 804 and a second port 818 that isin fluid communication with a second chamber 820 in the actuator body804. The first port and second port include hydraulic connections to theactuator. The hydraulic connection may include a first tube inside asecond tube such that the first port is the first tube, and the secondport is the annular area between the first tube and second tube. In analternate embodiment the hydraulic connection may include two adjacentports. However, other types and arrangements of connections could alsobe used.

The embodiment of FIG. 15 is similar to that of the embodiment of FIG.13 with the difference that the smart valve 806 is coupled to theactuator body 804 so that the axis of the smart valve (i.e. therotational axis of the integrated hydraulic motor-pump and electricmotor) 630 is perpendicular, or near perpendicular with the axis of theactuator body 632 as opposed to parallel to the axis of the actuatorbody 632. It is of course possible to mount the smart valve with itsaxis 630 at any angle between the parallel and perpendicular with thatof the actuator body axis 632. Therefore, it should be understood thatthe hydraulic motor-pump may be coupled to the actuator body in anyappropriate orientation and at any appropriate location.

FIG. 16 shows an embodiment of a smart valve 902 similar to thatdisclosed in FIG. 15. This embodiment shows a smart valve 902 includinga housing 904 coupled with a controller module 906. The controllermodule is situated on the top of the smart valve 902. The smart valveassembly includes a hydraulic motor-pump assembly (e.g. an HSU) 908closely coupled to a rotor 910 of an electric motor/generator. Thestator 912 of the electric motor/generator is rigidly connected to thehousing 904 of the electro-hydraulic valve assembly 902. The hydraulicmotor-pump includes a first port 914 that is in fluid communication witha first chamber of the actuator and a second port 916 that is in fluidcommunication with a second chamber of the actuator. The second port 916is also in fluid communication with fluid 918 that is contained withinthe volume of the housing 904. The hydraulic motor-pump and electricmotor/generator assembly are contained and operated within the fluid 918contained in the fluid filled housing 904.

The controller module 906 is connected to the electric motor/generatorvia an electronic connection 920 and is separated from the hydraulicfluid by a bulkhead 922, or other appropriate pressure sealed barrier.The electronic connection 920 is isolated from the hydraulic fluid via apass through 924. Within the controller cavity is a logic subassembly932, a power pack 934, and a capacitor 936. In another embodiment thepower pack 934 can be mounted to a dedicated heat sink that is thermallydecoupled from the hydraulic valve assembly 902. A power storage unit ismounted on the side of the hydraulic valve assembly 902, or it can beintegrated with the power pack 934. In yet another embodiment, the powerpack 934 is split into three subunits with each subunit housing a singleleg (half bridge) of the power pack. However, other arrangements arealso possible. For the purpose of minimizing thermal load and volume,the logic subassembly may be subdivided into a logic power module, asensor interface module, and a processor module. In one embodiment thelogic subassembly 932 uses a position sensor 938. The position sensormay share the same printed circuit board (PCB) that is used for housingFETs (IGBTs) or may be mounted on a flex cable. In another embodimentthe logic subassembly 932 may be completely sensorless. Furthermore,while a subdivided controller has been described above, it should beunderstood that all the components of the controller module 906 can beintegrated into a single assembly and produced on a single PCB.

In one embodiment, a rotary Hall effect position sensor 938 thatmeasures the rotational position of a source magnet 940 that isdrivingly connected to the electric motor/generator rotor 910, ismounted directly to the logic board 932. The Hall effect position sensormay also be protected from the working hydraulic fluid of theelectro-hydraulic valve assembly 902 by a sensor shield 942.

FIG. 17 depicts one embodiment of a controller-valve integration inschematic form. A pressure barrier 1002 separates a fluid-filledpressurized reservoir 1004 from air-filled controller compartment 1006that is exposed to atmospheric pressure. The pressure barrier 1002deflects within the boundaries 1008 under the influence of variablepressure within volume 1004 while motor 1010 and a controller board 1012remain stationary. A feed-through 1014 and a motor connection 1016 areelectrically connected to opposite ends of a flexible printed circuitboard 1018. When the pressure barrier 1002 flexes under the influence ofa variable pressure, it pulls feed-through 1014 with it which may applya force to a flexible printed circuit board 1018 which bends toaccommodate this movement without transferring the force to a motorconnection 1016. This may help to ensure reliable operation of thecorresponding solder joints. A controller board 1012 may be rigidlyattached to a valve housing 1020 and is restricted from motion whilefeed-through 1014 moves in conjunction with the motions of the pressurebarrier 1002 (e.g. a membrane or other construction). Flexible leaves1022 are welded 1024 or otherwise electrically connected to feed-throughpins 1026. Flexible leaves 1022 may accommodate motions of afeed-through 1014 and prevent transfer of reciprocal forces to thecontroller board 1012. A radially magnetized magnet 1033 may transferangular position of a rotor 1028 to a transducer module device 1030 viamagnetic flux permeable window 1032.

In some embodiments, flexible leaves 1022 may be solder joined withfeed-through pins 1026 using a low-temperature solder joint 1024. Thismay enable a self-healing behavior of flexible high current connections.Specifically, when 1024 develops micro-cracks, resistance of thecorresponding solder joint increases causing a localized temperaturerise and re-melting of the low temperature solder. This may be combinedwith non-wetting plating applied to the surrounding solder andconnection pads outside of the solder joint to prevent reflow of themolten solder away from the designated solder area.

FIG. 18 is a schematic of one embodiment of a smart valve architecture.The rotor shaft 1102 is operatively coupled to the shaft of a hydraulicmotor-pump 1104 that may be both bidirectional and backdrivable.However, embodiments in which the hydraulic motor-pump is unidirectionaland/or pumping only are also contemplated. The angular position of arotor shaft 1102 that is rigidly connecting a hydraulic pump 1104 to amotor 1106 may be used in a motor control loop as described elsewhere.The aforementioned position measurement is derived from a radiallymagnetized permanent magnet inducer 1108 which is rigidly attached to arotor shaft 1102 that is operationally located in fluid-filled reservoir1110. A magnetic field flux induced by an axially rotated magnet 1108penetrates through a magnetically transparent window 1112 that is builtinto a membrane 1114. The membrane separates the fluid filled reservoir1110 from the electronic enclosure 1116 that is exposed to atmosphericpressure. It should be noted that the membrane 1114 is exposed to avariable differential pressure between the fluid-filled and air exposedenclosures resulting in a variable membrane deflection. Magnetic flux1118 interacts with a field sensitive transducer 1120 that translates astrength of the measured magnetic flux 1118 into an angular position ofa rotor shaft 1102.

In one embodiment, a controller module 1130 includes a processor module1133, a storage capacitor 1134, a three-phase rectifier 1131 and a3-Phase power bridge 1132. A three-phase rectifier 1131 and a 3-Phasepower bridge 1132 are operatively connected to a motor 1106 via abidirectional 3-Phase feed 1135. A controller 1130 is powered by adirect voltage power source via a power feed 1141 and may be incommunication with at least one other similar controller or a centralvehicle suspension controller via a communication bus 1140. Though othertypes of communication including wireless communication might also beused. The specifics of the aforementioned architecture, algorithm, andcorresponding implementation are described elsewhere. Duringregenerative events associated with vertical wheel motions, or otherappropriate motions of a hydraulic actuator, fluid is forced through thehydraulic motor-pump 1104 producing rotary motion of an electric motor1106 that results in generation of back electromotive force (BEMF) onthe electric motor's terminals. In case of a power bus failure, whichmay be manifested in “starving” a DC power feed 1141, the BEMF isrectified in 1131 and its energy is stored in a capacitor 1134 that isconnected between positive and negative terminals of a power source.Therefore, charging of the capacitor 1134 results in developing asufficient voltage to power logic of a controller 1130 that is alsoconnected between positive and negative terminals of the capacitor 1134.A control algorithm implemented on a processor 1133 responds to afailure by either closing all switches in the bridge 1132 or bymodulating the duty cycle of the bridge to maintain a desired currentthrough the windings of a motor 1106 and producing a minimum fail-safetorque resulting in a safe damping force. Similarly, in case of afailure of a communication bus 1140, the controller rolls-back to apassive damping mode and maintains a desired passive dampingcharacteristic of a suspension system. Furthermore, in case of acatastrophic failure of a controller 1130, the motor-pump assembly 1106,1102, and 1104 may spin out of control resulting in voltage rise on a DCbus indicating an unacceptable suspension failure; a shunt relayconnected across a DC bus as described elsewhere detects an “above safevoltage level” condition and closes the circuit shorting a DC bus andeffectively guaranteeing safe suspension damping.

A processor module 1133 of a controller module 1130 may receive aplurality of intrinsic, extrinsic and vehicle related information. Theintrinsic information may originate from within the smart valve housing1153 and/or the controller housing 1154 forming a complete smart valve1155.

An intrinsic sensors suite may include, but is not limited to at leasttwo motor current sensors 1117, a bus voltage 1119 and current 1118sensors, a differential pressure sensor 1111, an actuator bodyaccelerometer 1145, an ambient 1142, fluid 1144, and a FET temperaturesensor 1143. An extrinsic sensor suite 1150 may also include for examplea suspension position sensor 1151 and a body acceleration sensor 1152,where a suspension position sensor 1151 which communicates alongitudinal position of a wheel in reference to the vehicle's body, anda body accelerometer 1152 which communicates vehicle body motions inreference to an inertial reference system that may include a bodytranslational and/or rotational motion.

In the preferred embodiment vehicle related information may include, butis not limited to, steering, throttle, brake inputs, yaw rate,longitudinal acceleration, lateral acceleration, driver preferences, aswell as a plurality of inputs such as calculated instantaneousforce-velocity requirements. These inputs may be communicated to acontroller via communication bus 1140. The specifics of theimplementation have been described elsewhere. However, it should beunderstood that the above signals can be communicated to a controller1130 using any other suitable means including a direct routing ofindividual signals or utilizing a data over power lines protocol.Furthermore, suspension actuators are effectively a link between anindependently moving wheel and a vehicle body collectively affected by aplurality of actuator motions. Therefore, and without wishing to bebound by theory, an onset of a dynamic event in any wheel actuatorassembly affects the behavior of all actuators connected between theircorresponding wheels and the vehicle's body. Consequently, it may bebeneficial from a control perspective to have a predictive signaling ofany suspension event to all actuator controllers 1130. Thus, theactuator controllers in a vehicle may desirably be connected to anetwork to enable communicating the desired information. The networkingcan be achieved in a centralized fashion when each actuator uploads allinformation, including but not limited to time sensitive informationlike pressure ripples to a central controller, which in turn distributesthis information downstream to all actuator controllers in the networkto take an appropriate action. Alternatively, this may be accomplishedin a decentralized manner by homogeneously connecting all controllers inthe vehicle using any appropriate connection which may include, but isnot limited to, a CAN bus, a Token Ring bus or a Data Over Power Businterface.

Without wishing to be bound by theory, at any given moment in time theperformance of an electro-hydraulic actuator primarily depends on ahydraulic motor-pump and electric motor performance characteristics aswell as on power bus limitations, ambient temperature, electroniccomponents, and hydraulic fluid temperatures. Recoverable thermaldependencies and non-recoverable age-related degradations due tomechanical wear-out and chemical changes in fluid composition may betaken into account by a control algorithm or protocol. Specifically, ona short-term time scale current-to-torque conversion curves may beadjusted based on fluid viscosity change due to temperature variationsas well as on power handling capabilities of the electronics due to therising temperature of electronic components and the amount of availableenergy stored in the system. On a long-term time scale the adaptivecontrol algorithm may take into account an increased leakage due tomechanical wear out of a hydraulic pump 1104 components and/or a longterm viscosity change (due to chemical degradation) of a hydraulicfluid. The same sensor suites noted above, including, but not limited toa differential pressure sensor 1111, temperature sensors 1144, 1142 and1143 as well as the commanded and actual force-velocity responsereceived from extrinsic sensors may be utilized to adjust bothshort-term and long-term parameters of the actuator model. Long-termparameter adjustments may be stored in a FLASH memory unit 1137.

In the depicted embodiment, a first input of a differential pressuresensor 1111 is connected to a first port of a pump 1104, while a secondinput of a sensor 1111 is operatively connected to a second port of apump 1104. Power and output leads of a differential pressure sensor 1111penetrate from a fluid-filled reservoir 1110 through ahermetically-sealed path-into a controller compartment 1116 and conveysa voltage representation of a differential pressure across a pump 1104to a processor module 1133. A differential pressure value is correlatedwith a fluid temperature and a plant's (i.e. the object of control)force-velocity to calculate new system parameters that representshort-term and long-term system drift while long-term model changes maybe saved in the FLASH memory 1137.

In addition to the above, a differential pressure variation may be usedas an early forward-looking signal to indicate a pending reversal in aplant's motion direction. The latter usually happens when the electricmotor/hydraulic motor-pump assembly is crossing a zero RPM point androtational speed cannot be calculated based on rotor position sensingalone. Additionally, being a direct indication of a force applied to aplant, a differential pressure provides an unambiguous input to acontroller 1130 involved in a fast control loop in response to aninstantaneous pressure variation.

FIGS. 19A, 19B, 19C, 19D, 19E, and 19F show various embodiments ofconnection methods for integrating the smart valve with the activesuspension actuator body. In the embodiment of FIG. 19A a cross sectionthrough a smart valve 1202 and actuator body 1204 is shown where theactuator body has a protrusion 1206 extending out from the actuatorbody. The protrusion 1206 is formed so that it can accept and locate thebody of the hydraulic motor-pump 1208 such that the hydraulic connectionbetween the first port of the hydraulic motor-pump and first chamber ofthe actuator body is made via tube 1210. The protrusion 1206 may beconstructed by various means such as fixing a separate member to theactuator body (by welding for example), or by constructing the actuatorbody so that the protrusion is integrally formed with the actuator body(e.g. by utilizing a casting or a sheet metal forming process forexample). The open cavity 1212 created by the protrusion 1206 is influid communication with the second port of the hydraulic motor-pump andthe second chamber of the actuator body when connected thereto andserves to make the hydraulic connection between the two. An externalmember 1214 encloses the smart valve assembly 1202 and serves to rigidlysecure the smart valve assembly to the actuator body and to contain thefluid therein. The external member 1214 can be assembled and securedafter the smart valve assembly is connected to the actuator body by asuitable metal forming process (such as rolling or crimping for example)or by other means such as being secured by fasteners for example.

FIG. 19B shows an alternate embodiment of connecting the smart valve1202 to the actuator body 1204. In the depicted embodiment, the actuatorbody has a protrusion 1206 extending out from the actuator body which isconfigured to accept and locate the fluid filled housing of thehydraulic motor-pump 1216 so that the hydraulic connection between thefirst port of the hydraulic motor-pump and first chamber of the actuatorbody is made via an encapsulated connector tube 1214. The protrusion1206 may be constructed by various means such as fixing a separatemember to the actuator body (by welding for example), or by constructingthe actuator body so that the protrusion is integrally formed with theactuator body, (by utilizing a casting or a sheet metal forming processfor example). A second cavity 1218 (shown in FIG. 19C) is created in theprotrusion 1206 and is in fluid communication with the second port ofthe hydraulic motor-pump and the second chamber of the actuator body andserves to make the hydraulic connection between the two. The protrusion1206 can be secured after the smart valve assembly is connected to theactuator body by a suitable metal forming process such as a rollingprocess or crimping for example. The unformed state of the protrusion1206 is shown in FIG. 19B and is shown in the secured, formed state inFIG. 19C. In the embodiment of FIGS. 19B and 19C, the protrusion 1206 isformed over tabs 1218 that are formed into the fluid filled housing1216. In FIG. 19D the actuator body 1204 is shown without the smartvalve so that the openings 1220 and 1222 in the actuator body can beseen as well as to show the protrusion 1206 in the unformed state. Theopening 1220 in the actuator body 1204 encases the connector tubeconnector tube 1214 and the opening 1222 connects to the second port inthe hydraulic motor-pump via the fluid filled housing 1216. The opening1220 is also in fluid communication with the second chamber of theactuator. A seal or gasket (not shown) may be placed between theactuator body and the smart valve so as to seal the hydraulic fluidinternally from the openings 1220 and 1222 as well as to contain thefluid so that it cannot leak externally. An alternate securing shape ofthe protrusion 1206 is shown in FIGS. 19E and 19F. In the depictedembodiments, the protrusion 1206 is formed into a groove 1226 that isformed into the fluid filled housing 1218. The protrusion 1206 is shownin the unformed state in FIG. 19E and in the secured, formed state inFIG. 19F. It is possible to incorporate a thermally insulating memberbetween the actuator body and the smart valve if desired.

While particular methods and arrangements are described above forsecuring a smart valve to an actuator body, it should be understood thatthat other methods of securing a smart valve to an actuator body arealso contemplated.

FIG. 20 depicts an embodiment of a suspension installation 1302 of anactive suspension actuator 1304 within a wheel well at one corner of avehicle. The suspension system 1302 includes an active suspensionactuator 1304 integrated with a smart valve 1306 that is coupled betweenthe chassis 1308 and the wheel 1310. Generally, the chassis is commonlyreferred to as a sprung mass, while the wheel and mounting assembly arecommonly referred to as an unsprung mass. As illustrated, the wheel 1310is coupled to the chassis and actuator 1302 by an upper control arm1312, a lower control arm 1314 and a mounting member 1316 (which iscommonly referred to as the knuckle). The upper control arm 1312 andlower control arm 1314 are coupled to the chassis at connection points1318, while the actuator is coupled to the lower control arm 1314 via alower mounting member 1320 and to the chassis at an upper mountingmember 1322. The mounting members 1320 and 1322 may be in the form ofelastomeric bushings or other types of suspension mounts, such ashydramounts or active suspension bushings for example, that can beadapted to reduce noise or resonances that may be associated withoperation of the active suspension actuator being transmitted to thevehicle or to improve the vehicle NVH characteristics. As depicted inthe figure, a position sensor 1324 may be located between the suspensionmounting assembly and the chassis so that wheel position relative to thechassis can be monitored and used for control of the active suspensionactuator. An accelerometer 1326 may be mounted on the unsprung mass soas to monitor wheel acceleration and an accelerometer(s) 1328 may bemounted on the sprung mass so as to monitor chassis accelerations. Anaccelerometer, rotary position sensor, and/or pressure sensors may becontained within the active suspension housing and may be combined andadapted with the vehicle sensors to sense a wheel and/or body event.These signals may be used for control of the active suspension actuator.Many combinations of vehicle and actuator based sensors can beconstructed and arranged to sense a wheel and/or body event and used forthe control of the active suspension actuator. For example, appropriatesensor inputs may be related to wheel acceleration sensing, pressuresensing, position sensing, smart valve local sensing, rotary motorposition sensing, multi-sensor whole vehicle sensing, a centralized IMUsensor architecture, utilizing combinations of sensors per wheel andaxle, as well as other appropriate types of sensors.

The depicted smart valve is electrically connected to the vehicleelectrical power, control, and sensor systems via a connection 1330. Thecompact integrated active suspension actuator 1304 occupies a similarvolume as a typical passive and semi active damper, which facilitatesinstallation of the integrated system into a vehicle wheel well. In theembodiment shown in FIG. 20, the smart valve 1306 is positioned with itsaxis 630 parallel to the axis of the actuator body 632. However, otherpositions and orientations of the smart valve are also contemplatedinorder to facilitate installation in other vehicle locations as well asother possible applications.

FIG. 21 shows a schematic implementation of an embodiment of an activesuspension actuator 1402 with an integrated smart valve 1404 withchassis mounted power and signal wire connections. As depicted in thefigure, the actuator and smart valve are disposed in a vehicle wheelwell 1406. In this embodiment, the active suspension actuator withintegrated smart valve, 1402 and 1404, is attached to the unsprungportion of the suspension 1408, which connects the wheel 1410 to thevehicle chassis 1412, such that during operation, there is relativemotion between the smart valve 1404 and the chassis of the vehicle 1412.The smart valve's controller is connected to the chassis-mounted wiringharness 1414 via one or more flex cable pigtails 1416 and mating pair(s)of connectors 1418. The pigtails exit the controller housing through oneor more lead-out glands 1420 that provide strain relief as well asenvironmental sealing. Both sides of the mated pair of connectors areattached to a chassis-mounted bracket 1422 and their cables includestrain reliefs connected to the same bracket to minimize any motionacross the connection, whether it be due to shock, vibration, or cableflexing. The same approach can be used to wire local sensors and othercomponents to the actuator-mounted smart valve controller as well.

FIG. 22 depicts an alternate location of a smart valve on an actuatorbody. In the embodiments of FIGS. 13, 15 and 20 the smart valve islocated on the side of the actuator body. However, the smart valve maybe mounted in other locations on the active suspension actuator as well.One such location may be at the external end of the piston rod where itis fixed to the chassis member. The embodiment of FIG. 22 depicts thesuspension installation 1502 of an active suspension actuator 1504within the wheel well at one corner of a vehicle. The suspension system1502 includes an active suspension actuator 1504 integrated with a smartvalve 1506 that is coupled between the chassis 1508 and the wheel 1510.In the embodiment depicted in FIG. 22 the smart valve 1506 is located atthe external end of the piston rod 1512. The axis of the hydraulicmotor-pump 630 may be co-axial with the axis of the actuator 632, andmay be fixed to a suspension mount 1514 which is connected to thechassis 1508. In this arrangement the first port and second port of thehydraulic motor-pump contained within the smart valve is in fluidcommunication with the first chamber and second chamber of the actuatorvia hydraulic flow passages formed in the piston rod 1512. The smartvalve is electrically connected to the vehicle electrical power, controland sensor systems via a connection 1516.

The arrangement depicted in FIG. 22 may be advantageous as the smartvalve now occupies the space at the top of the suspension where the topsuspension mount normally connects to the chassis, and as such manyvehicle chassis construction have adequate clearance in this area.Another advantage is that the smart valve is not connected to thechassis and does not move with the wheel, thereby reducing the unsprungmass of the suspension, as well as mitigating a possible need for flexcables. While an embodiment where the smart valve is located coaxiallywith, and adjacent the top suspension mount of, the hydraulic actuator,embodiments in which the smart valve is located at or adjacent to abottom mount of the hydraulic actuator are also contemplated.

The embodiments shown in FIGS. 20 and 15 depict a suspension arrangementwhere an upper and lower suspension member is used to locate the wheelassembly relative to the chassis. However, in an alternative embodiment,the active suspension actuator with integrated smart valve may beadapted into a McPherson strut arrangement, not depicted. In such anarrangement, the actuator body and piston rod may become a locatingmember of the wheel assembly. It is also possible to adapt the activesuspension actuator to incorporate other arrangements such as anintegral air spring, coil spring, torsion spring leaf/beam springs, aninverted actuator, a telescoping actuator, a self-pumping ride heightadjustable device, or to incorporate alternate actuator arrangementssuch as monotube, twin tube, and/or triple tube configurations as thedisclosure is not so limited.

FIG. 23 is a schematic representation of one embodiment of a suspensionsystem adapted to provide on demand energy. As illustrated in thefigure, an on-demand energy controller 1600 is operatively coupled to anelectric motor 1602 such that it controls a motor input of the electricmotor. The electric motor 1602 is operatively coupled to a hydraulicmotor-pump 1604 which is coupled to a hydraulic actuator 1606. Actuationof the hydraulic motor-pump 1604 controls a fluid flow into and out ofthe various portions of the actuator 1606 to create an actuation forceof the actuator. The system also includes at least one sensor 1608 whichis in electrical communication with the on-demand energy controller1600. The sensor is adapted to detect one or more system conditions andprovide that information to the on-demand energy controller so that thecontroller can control the overall suspension system to respond to thatsensor input. While this system has been described with regards to anon-demand energy suspension system, it should be understood that anyhydraulic actuator could also implement an on-demand energy controlsystem as described elsewhere.

FIGS. 24 and 25 are directed to embodiments of a suspension system thatagain includes a controller 1600, an electric motor 1602, a hydraulicmotor-pump 1604, and a hydraulic actuator 1606. However, as depicted inthe figures, unlike previous embodiments where they are directlyconnected, or closely coupled to one another, a fluid connection betweenthe hydraulic actuator 1606 and the hydraulic motor-pump 1604 mayinclude one or more valves 1610 as well as hydraulic tubes or hoses1612. Depending on the particular embodiment, the hydraulic motor-pump1604 may still be located near, or be attached to, the hydraulicactuator 1606 and include valves 1610 within or proximal to thehydraulic actuator 1606. However, embodiments in which the hydraulicmotor-pump is remotely located from the hydraulic actuator 1606 are alsocontemplated. Regardless of the use of the one or more valves 1610 andthe hydraulic tubes or hoses 1612, the electric motor 1602 may still becontrolled in a manner as noted previously in order to dynamicallycontrol the system and provide on-demand energy and/or control withinthree or more quadrants of a force velocity domain.

In addition to the above, FIG. 25 also includes a compliant mechanism1614 located in series with the hydraulic actuator 1606, as well as adamper 1616 located in parallel with the hydraulic actuator 1606. Thecompliant mechanism may be a spring (e.g. a coil spring, air spring, orother appropriate spring) or an elastomeric bushing (e.g. a suspensiontop mount or bottom mount) or any other appropriate mechanism capable offunctioning like a spring. Additionally, the damper 1616, which islocated in parallel with both the hydraulic actuator 1606 and thecompliant mechanism 1614, may either be a semi-active damper or apassive damper as the disclosure is not so limited. Again, the electricmotor 1602 may still be controlled in a manner as noted previously inorder to dynamically control the system and provide on-demand energyand/or control within three or more quadrants of a force velocitydomain. In one embodiment the controller may control the motor 1602 andone or more semi-active valves in the damper 1616 such that they arecoordinated to operate in unison to affect body and/or wheel control. Insome embodiments one or more valves 1610 are included that areelectronically controlled and/or coordinated by the controller.Additionally, in certain embodiments, additional passive valves such ascompression and rebound blowoff valves, which may reside on the pistonhead, not depicted, may also be included.

In some embodiments, the one or more valves 1610 depicted in FIGS. 24and 25 and described above may correspond to the specific valvingarrangements shown in FIGS. 26A-26D and as described in more detailbelow.

FIG. 26A depicts an embodiment where the hydraulic tubes or hoses 1612are direct connections and the one or more valves 1610 are not used.

FIG. 26B presents an embodiment where the one or more valves 1610include a blowoff valve 1618 (which may comprise separate rebound andcompression digressive valves, which may further feature substantiallyno leakage below a first pressure threshold, a top diverter valve 1620for use during rebound, and a bottom diverter valve 1622 for use duringcompression. The diverter valves provide fluid communication between theactuator volumes and the hydraulic motor-pump 1604 when fluid velocityis below a threshold, and provide dual communication between both thehydraulic motor-pump and a bypass channel when the fluid flow velocitythreshold is exceeded. The bypass channel may further comprise a tunedrestrictive valve to provide damping.

FIG. 26C depicts an embodiment where the one or more valves 1610correspond to a controlled H-bridge rectifier 1624 that controls thefluid flow through the hydraulic hoses or tubes 1612. The H bridgerectifier 1624 includes electronically controlled valves, such as asolenoid valve or other appropriate valve. Additionally, a check valvemay be located in parallel to each electronically controlled valve, notdepicted, such that external movement into the hydraulic actuator 1606may allow fluid to flow from the actuator body, through the checkvalves, towards the hydraulic motor-pump. These reverse check valvesprovide regenerative operation such that external input to the actuatorcreates a rotation of the hydraulic motor-pump 1604.

FIG. 26D depicts an embodiment of the one or more valves 1610 includingan electrically controlled valve 1626 located on one hydraulic tube orhose 1612 and another electrically controlled valve 1626 controllingflow of fluid between both of the hydraulic tubes or hoses 1612. Theembodiment also includes several passive check valves 1628 to controlfluid relative to the electrically controlled valves 1626 and the twohydraulic hoses or tubes 1612 so that in an actuated compression stroke,on-demand fluid pressure acts on the annular area (piston area minus thepiston rod area), and in an actuated extension stroke, on-demand fluidpressure acts on the piston rod area. The presence of such valving inaddition to on-demand energy control may improve inertia response of thesystem, provide unidirectional flow, and improve harshnesscharacteristics of some embodiments. In such embodiments force on theactuator may be created by a pressure in the actuator 1606 that is atleast partially decoupled from the pressure created by the hydraulicmotor-pump. The hydraulic motor-pump may be operated at high bandwidth(such as on a per wheel or body event basis), while the electronicallycontrolled valving may also operates at least this frequency. Whilespecific valving arrangements are described above, it should beunderstood that embodiments using other types of valving arrangementsand/or no separate valving other than that provided by a smart valve arealso contemplated.

FIG. 27 is directed to an embodiment of a suspension system that againincludes a controller 1600, an electric motor 1602, a hydraulicmotor-pump 1604, and a hydraulic actuator 1606. The embodiment alsoincludes a low pressure reservoir or accumulator 1630 in fluidconnection with a first port of the hydraulic motor-pump 1604. A fluidconnection between the hydraulic actuator 1606 and a second port of thehydraulic motor-pump 1604 may include one or more valves 1610 as well ahydraulic tube or hose 1612. Depending on the particular embodiment, thehydraulic motor-pump 1604 may still be located near, or be attached to,the hydraulic actuator 1606. However, embodiments in which the hydraulicmotor-pump is remotely located from the hydraulic actuator 1606 are alsocontemplated. Regardless of the use of the one or more valves 1610 andthe hydraulic tube or hose 1612, the electric motor 1602 may still becontrolled in a manner as noted previously in order to dynamicallycontrol the system and provide on-demand energy and/or control withinthree or more quadrants of a force velocity domain. In the embodimentdepicted the actuator is a single acting actuator, wherein the one ormore valves may contain a check valve that checks against flow of fluidfrom the single acting actuator to the hydraulic motor-pump. This checkvalve may be in parallel to an electrically controlled valve thatcontrols flow of fluid from the single acting actuator to the hydraulicmotor-pump. In another embodiment, a single electrically controlledvalve may control flow of fluid to and from the single acting actuatorand the hydraulic motor-pump. The non-controlled side of the singleacting actuator may be open to atmospheric pressure or may contain a lowpressure gas. The hydraulic connection 1612 may connect to a compressionside of the actuator or to the extension side of the single actingactuator.

In some embodiments, the system depicted in FIG. 27 may be controlled asfollows: to create an active extension force, the controller 1600creates a torque in the electric motor 1602, which puts a torque on thehydraulic motor-pump 1604, creating pressure. The pump may operate in aforward direction, wherein pressure from the hydraulic motor-pump movesfluid in a first direction from the hydraulic motor-pump, through thevalve 1610 (such as a check valve free flow path), and into thecontrolled side of the actuator thus creating an extension force. Thisextension force operates on a compliant mechanism 1614 that will bedescribed below. To create a compression compliance, during which theactuator provides a substantially low force, the valve 1610 may becontrolled by the controller 1600 to open (such as an electronicallycontrolled solenoid or servo valve), allowing fluid to flow from thecontrolled side of the actuator to the hydraulic motor-pump 1604, andinto the reservoir 1630. In this case, the electric motor is backdrivensuch that energy may flow from the motor into the controller in aregenerative mode of operation. In one control mode, the electric motormay control the hydraulic motor-pump to actively pump fluid from thecontrolled side of the actuator to the reservoir 1630. By controllingtorque in the motor dynamically (and in some embodiments in conjunctionwith valves in 1610), an instantaneous force may be provided to thesuspension.

In another embodiment, the system of FIG. 27 may be accomplished withoutany valve 1610, such that holding force is accomplished by directlycontrolling the electric motor 1602. One possible benefit of usingvalving, however, is to provide low energy holding force operation.

In addition to the above, FIG. 27 also includes a compliant mechanism1614 located in series with the hydraulic actuator 1606, and a damper1616 located in parallel with the hydraulic actuator 1606. The compliantmechanism may be a spring (e.g. a coil spring, air spring, or otherappropriate spring) or an elastomeric bushing (e.g. a suspension topmount or bottom mount) or any other appropriate mechanism capable offunctioning like a spring. Additionally, the damper 1616, which islocated in parallel with both the hydraulic actuator 1606 and thecompliant mechanism 1614, may either be a semi-active damper or apassive damper as the disclosure is not so limited. Again, the electricmotor 1602 may still be controlled in a manner as noted previously inorder to dynamically control the system and provide on-demand energyand/or control within three or more quadrants of a force velocitydomain.

FIG. 28 is a graph showing the control and tuning regimes for oneembodiment of an active suspension system capable of providing on demandenergy flow as described herein. In addition to operating within thefour quadrants of the force velocity domain, the graph also indicatesregions corresponding to roll holding force, pressure blowoff (which maybe individual valves for each of compression and rebound), high-speedvalving (such as a diverter valve described elsewhere in thisspecification), and software power limits (such as controlling a maximumcurrent or a maximum current times velocity in the motor controller).These various concepts are described in more detail elsewhere.

In some embodiments, a hydraulic actuator and/or suspension system isassociated with an electronics architecture that uses an energy bus withvoltage levels that can be used to signal active suspension systemconditions. For example, an active suspension with on demand energydelivery may be powered by a loosely regulated DC bus that fluctuatesbetween about 40 and 50 volts. When the bus is below a lower threshold,for example, 42 volts, the active suspension controller for eachactuator may reduce its energy consumption by operating in a moreefficient state, reducing the amount of force it commands, and/orreducing how long it commands a force (e.g. during a roll event, thecontroller allows the vehicle to increasingly lean by relaxing theanti-roll mitigation to save energy). Additionally, a lower voltage maysignal the active suspension actuators to bias towards a regenerativemode if the actuator is capable of energy recovery. Similarly, when ahigh voltage is detected, the actuators may reduce energy recovery ordissipate damping energy in the windings of a motor in order to preventan overvoltage condition. While this example was described usingthresholds, it may also be implemented in a continuous manner whereinthe active suspension is simply controlled as some function of thevoltage of its power bus. Such a system may have several advantages. Forexample, allowing the voltage to fluctuate increases the usable capacityof certain energy storage mechanisms such as super capacitors on thebus. It may also reduce the number of data connections in the system, orreduce the amount of data that needs to be transmitted over dataconnections such as CAN. In some embodiments the power bus may even beused to transmit data through a variety of communication of power linemodulation schemes in order to transmit data such as force commands andsensor values.

In another embodiment, an active suspension as described above isassociated with a vehicular high power electrical system that operatesat a voltage different from (e.g. higher than) the vehicle's primaryelectrical system. For example, multiple active suspension power unitsmay be energized from a common high power electrical bus operating at avoltage such as 48 volts, with a DC/DC converter between the high powerbus and the vehicle's electrical system. Several devices in addition tothe active suspension may be powered from this bus, such as, forexample, the electric power steering (EPS). In such an embodiment, thehigh power bus is galvanically isolated from the vehicle's primaryelectrical system using a transformer-based DC/DC converter between thetwo buses. In some embodiments the high power electrical system may beloosely regulated, with devices allowing voltage swing within somerange. In some embodiments the high power electrical system may beoperatively connected to an appropriate form of energy storage such ascapacitors and/or rechargeable batteries. These energy storage devicescan be directly connected to the bus and referenced to ground; connectedbetween the vehicle electrical system and the high power electricalsystem; or connected via an auxiliary DC/DC converter. Certain otherconnections may also exist, including, for example, a split DC/DCconverter connecting the vehicle electrical system, the high power bus,and the energy storage.

Without wishing to be bound by theory, combining an active suspensionwith a power bus that is independent of the vehicle's electrical systemmay provide several advantages. First, the vehicle's electrical systemmay be isolated from voltage spikes and electrical noise from high powerconsumers such as suspension actuators. The DC/DC converter may be alsobe adapted to employ dynamic energy limits so that too many loads do notovertax the vehicle's electrical system. By running the high power busat a voltage higher than the vehicle's electrical system, the system mayalso operate more efficiently by reducing current flow in the powercables and the motor windings. In addition, the active suspensionactuators may be able to operate at higher velocities for a given motorwinding.

In some embodiments, the suspension systems described above, areassociated with an active safety system adapted to control thesuspension system to improve the safety of the vehicle during acollision or dangerous vehicle state. In one exemplary embodiment, thesuspension system is controlled to deliver a vehicle height adjustmentwhen an imminent crash is detected in order to ensure the vehicle'sbumper collides with the obstacle (for example, a stopped SUV ahead) soas to maximize the crumple zone or minimize the negative impact on thedriver and passengers in the vehicle. In such an embodiment, thesuspension may adjust to a set ride height to optimize performanceduring any sort of pre or post-crash scenario. In another embodiment,the suspension system can adjust wheel force and tire to road dynamicsin order to improve traction during ABS braking events or electronicstability program (ESP) events. For example, the wheel can be pushedtowards the ground to temporarily increase the contact force (byutilizing the vertical inertia of the vehicle). This may either besustained for a predetermined duration or it may be pulsed over multipleshorter durations as the disclosure is not so limited.

In the above noted embodiments, the suspension systems as describedherein can be utilized to rapidly change the energy and performancedelivered by the suspension on a per event basis in order to respond toan imminent safety threat. By exploiting the fast response timecharacteristics of these suspension systems in combination with anactive safety system, where corrective action often has to occur inabout 100 ms or less, vehicle dynamics such as height, wheel position,and wheel traction, may be rapidly adjusted and can operate in unisonwith other safety systems and controllers on the vehicle to increasevehicle safety.

In one specific embodiment, a suspension as described herein is used asan active truck cab stabilization system to improve comfort, among otherbenefits. In one embodiment geared towards European-design trucks, fourhydraulic actuation systems are disposed between the chassis of a heavytruck and the cabin. A spring sits in parallel with each actuator (i.e.coil spring, air spring, or leaf spring, etc.), similar to the springand actuator depicted in FIG. 5, and each assembly is placed roughly atthe corner of the cabin. Sensors on the cabin and/or the chassis sensemovement, and a control loop controlling the active suspension commandsthe actuators to keep the cabin roughly level. In an embodiment forNorth American-design trucks, two actuators are used at the rear of thecabin, with the front of the cabin hinged to the chassis. In someembodiments such a suspension may contain modified hinges and bushingsto allow greater compliance in yaw, pitch, and/or roll. In a relatedembodiments, a suspension system incorporating this type of hydraulicactuators may be applied in other appropriate applications, such as, forexample, on an isolated truck bed or trailer to reduce vibrationtransferred to the truck load. Here, the system might employ two activeactuators to stabilize the cab. The system uses a plurality of sensors(e.g. accelerometers) and/or vehicle data (e.g. steering angle) in orderto sense or predict cab movement, and a control system sends commands tothe actuators in order to stabilize the cab. Such cab stabilizationprovides significant improvement in comfort and may reduce maintenancerequirements in the truck.

In another related embodiment, a single hydraulic actuator may becoupled to a suspended seat such as, for example, a truck seat. In thisembodiment, the seat rides on a compliant device such as an air spring,and the actuator is connected in parallel to this complaint device.Sensors measure acceleration and control the seat height dynamically toreduce heave input to the individual sitting on the seat. In someinstances the actuator may be placed off the vertical axis in order toaffect motion in a different direction. By using a mechanical guide,this motion might not be limited to linear movement. In addition,multiple actuators may be used to provide more than one degree offreedom for controlling movement of the seat.

A long haul truck containing an active suspension may especially benefitby improving driver comfort and reducing driver fatigue. By using anactive suspension with on demand energy delivery, the system can besmaller, easier to integrate, faster response time, and more energyefficient.

In another embodiment, a suspension system as described herein isassociated with an air spring suspension in which static ride height isnominally provided by a chamber containing compressed air. In such oneembodiment, the hydraulic actuator of the suspension system isincorporated in a standard hydraulic triple tube damper, with aside-mounted hydraulic motor-pump and electric motor, which may or maynot be integrated with the housing as described above. The hydraulicmotor-pump and electric motor may be placed towards the base of theactuator body such that an airbag with folding bellows can fit aroundthe actuator on an upper portion of the housing. In such an embodiment,a standard air suspension airbag can be placed about the actuator bodytowards the top of the unit. In another embodiment, the suspensionsystem includes hoses exiting the hydraulic actuator housing near thebottom and leading towards an external power pack containing a hydraulicmotor-pump and an electric motor. As such, the physical structures ofthe active suspension actuator and the air spring can again be joined onthe top of the housing.

In a related embodiment, the control systems for a suspension system andan air suspension system may either be in electrical communication withone another or integrated together. In such an embodiment, air pressurein the air suspension may be controlled in conjunction with thecommanded force in the hydraulic actuator of the suspension system. Thiscombined control may either be for the entire air spring system, or itmay be implemented on a per-spring (per wheel) basis. The frequency ofthis control may be on a per event basis and/or based on general roadconditions. Generally, the response time of the active suspensionactuator is faster than the air spring, but the air spring may be moreeffective in terms of energy consumption at holding a given ride heightor roll force. As such, a controller may control the active suspensionfor rapid events by increasing the energy instantaneously in theon-demand energy system, while simultaneously increasing or decreasingpressure in the air spring system, thus making the air springeffectively an on-demand energy delivery device, albeit at a lowerfrequency. By combining the controlled aspects of an active suspensionthat uses on-demand energy with an air spring that can also becontrolled to dynamically change spring force, greater forces may beachieved in the suspension, adjustments can be made more efficiently,and the overall ride experience can be improved.

In some embodiments, a suspension system as described herein is coupledwith one or more anti-roll bars in a vehicle. In one specificembodiment, a standard mechanical anti-roll bar is attached between thetwo front wheels and a second between the two rear wheels. In anotherembodiment a cross coupled hydraulic roll bar (or actuator) is attachedbetween the front left and the rear right wheels, and then anotherbetween the front right and the rear left wheels. Since the activesuspension will often counteract the roll bar during wheel events, itmay be desirable for efficiency and performance reasons to completelyeliminate the roll bar (wherein the active suspension with on demandenergy acts as the only vehicular roll bar), or to attach a novel rollbar design. In one embodiment, a downsized anti roll bar is disposedbetween the wheels, such that there is a large amount of springcompliance in the bar. In another embodiment, an anti roll bar withhysteresis is disposed between the two front and/or the two rear wheels.Such a system may be accomplished with a standard roll bar that has arotation point in the center of the roll bar, wherein between two limitsthe two ends of the bar can twist freely. When the twist reaches someangle, a limit is reached and the twist becomes stiff. As such, forcertain angles between some negative twist and some positive twist fromlevel, the bar is able to move freely. Once the threshold on either sideis reached, the twist becomes more difficult. Such a system can befurther improved by using springs or rotary fluid dampers such thatengagement of the limit is gradual (for example, prior to reaching thelimit angle a spring engages and twist resistance force increases),and/or it is damped (e.g. using a dynamic mechanical friction or fluidmechanism).

In another embodiment, a suspension system may be coupled with an activeroll stabilizer system. The active roll stabilizer system may either behydraulic, electromechanical, or any other appropriate structure.

Use of anti-roll bar technologies and/or active roll stabilizer systemsin connection with the suspension system, and especially an activesuspension, as described herein may be especially beneficial when avehicle experiences high lateral accelerations where roll force isgreatest and may exceed a maximum force capability of the suspensionactuator. Thus, by implementing anti-roll bar technologies and/or activeroll stabilizer systems that primarily operate at higher accelerations,roll force levels, and/or roll angles as compared to the suspensionsystem, roll performance can be improved. While several technologies aredisclosed to assist in mitigating vehicle roll, the disclosure is notlimited in this regard as there are many suitable devices and methods ofproviding an anti-roll force to supplement a suspension.

As noted above, it is desirable to provide a fast response time foreither a hydraulic actuation system and/or a suspension system. However,without wishing to be bound by theory, inertia of the actuation systemitself and components associated with it may impact the ability torespond quickly due to inertial forces limiting the response of thesystem. Consequently, in some embodiments, it is desirable to mitigatethe impact of the system inertia on a response of the system. Asdescribed in more detail below, this may be accomplished in a variety ofways.

In one embodiment, a hydraulic actuation system and/or a suspensionsystem includes rotary elements made from low inertia materials in orderto reduce the amount of energy needed to accelerate these elements andthus increase the response time of the system. For example, thehydraulic pump and/or motor shaft may be produced from an engineeredplastic with a lower mass in order to reduce rotary inertia. This mayalso have an additional benefit for systems including a positivedisplacement pump by reducing the transmissibility of high frequencyinputs into the actuator (i.e. a graded road at high speed input on thewheel). In another exemplary embodiment, a system might include alow-inertia hydraulic motor-pump such as a gerotor. In addition, theelectric motor coupled to the hydraulic pump may also have a lowinertia, such as by using an elongated but narrow diameter rotor of themotor. In one such embodiment, the diameter of the rotor is less thanthe height of the rotor. Additionally, a system may use features such asbearings, a low startup torque hydraulic motor-pump, or hydrodynamicbearings in order to reduce startup friction of the rotating assembly.

In another embodiment, a hydraulic actuation system or suspension systemincludes an inertia buffer located in series to help mitigate inertialeffects. The inertia buffer may either be located externally tohydraulic actuator, or it may be integrated into the hydraulic actuatoras the disclosure is not so limited. An inertia buffer may be embodiedin a number of different ways. For example, an inertia buffer may beembodied as fluid leakage around the hydraulic motor-pump, anappropriately sized orifice arranged in parallel with the hydraulicmotor-pump, an elastic coupling between the hydraulic motor-pump andelectric motor, a damper and spring combination located between thepiston head and actuator body, an active bushing, and/or any otherappropriate device or configuration capable of at least partiallydecoupling movement of the electric motor, hydraulic motor-pump, and/orhydraulic actuator from one another.

In yet another embodiment, the hydraulic actuation system and/or asuspension system is controlled using an algorithm to both predict andcompensate for inertia of the system. In such an embodiment, thealgorithm predicts inertia of the electric motor and/or hydraulicmotor-pump and controls the a motor input of the electric motor, e.g. amotor torque, to at least partially reduce the effect of inertia on aresponse of the system. For example, for a hydraulic active suspensionincluding a hydraulic motor-pump operatively coupled to an electricmotor, a fast pothole hit to a wheel will create a surge in hydraulicfluid pressure and accelerate the hydraulic motor-pump and electricmotor. However, an inertia of the rotary elements, which are thehydraulic motor-pump and electric motor in this case, will resist thisacceleration, creating a force in the actuator. This force willcounteract compliance of the wheel. This may create harshness in theride of the vehicle, and may be undesirable. In contrast, a systememploying predictive analytic algorithms may factor inertia of thevarious rotary elements into the active suspension control and maycommand a motor torque that is lower than the desired torque duringacceleration events, and at a higher torque that the desired torqueduring deceleration events. The delta between the command torque of themotor and the desired torque (such as the control output from a vehicledynamics algorithm) is a function of the rotor or actuator acceleration.Additionally, the mass and physical properties of the rotor may beincorporated in the algorithm. In some embodiments acceleration iscalculated from a rotor velocity sensor (by taking the derivative), orby one or two differential accelerometers on the suspension. In somecases the controller employing inertia mitigation algorithms mayactively accelerate the mass.

Without wishing to be bound by theory, certain hydraulic motors-pumps,such as a gerotor, produce a pressure ripple during operation. Dependingupon the frequency of operation, this pressure ripple may result invibrations that are either audibly or physically noticeable.Consequently, in some embodiments, a hydraulic actuation system and/or asuspension system may include an appropriate ripple cancellation methodand/or device. For example, a motor input of the electric motor may becontrolled to produce a varying pressure with a profile similar to thepressure ripple but 180° out of phase. In another exemplary embodiment,position-timed ports communicating with a chamber containing acompressible medium is used to reduce the pressure ripple. Other methodsof reducing a pressure ripple might also be used as the disclosure isnot so limited.

Example: Controlling an Active Suspension System in Response to WheelEvents

FIG. 8 demonstrates an active suspension motor torque 402 control systemthat updates in response to wheel events determined from sensed bodyacceleration 400. As can be seen in the chart, changes to the commandedmotor torque 402 occur at a similar frequency over the presented timeperiod to body acceleration 400, which is caused by wheel events such asbumps, hills, and potholes, and driver inputs such as turns, braking,etc.

FIG. 9 shows the same data in terms of frequency instead of time. Theshape of the motor torque 408 magnitude command with respect tofrequency roughly traces the shape of the body acceleration 406magnitude with respect to frequency. This trace of the control algorithmdemonstrates that not only is commanded motor torque updated atfrequencies at least as high as wheel events are occurring, but alsothat there is high correlation between the motor torque magnitude andthe body acceleration magnitude.

Example: System Natural Frequency Derivation

As noted above in some embodiments, it is desirable for a hydraulicactuation system and/or suspension system to respond quickly to commandsbecause it directly affects the ability of the system to operate in aclosed-loop control system.

Referring to FIG. 10, in a feedback loop, the time from receiving anexternal command 500, commanding a desired output 502, and the physicalsystem subsequently responding at 504 affects the maximum frequency atwhich the overall system can be controlled (its bandwidth). This is inaddition to response times associated with subsequent sensing andcommands at 506 to obtain a desired output at 508 using the closed loopcommand structure. Therefore, and without wishing to be bound by theory,the ability of a closed-loop system to respond to high frequency inputs(by either rejecting them or following them), will be limited in part bythe actuator's response time.

The system response time can be characterized in many different ways,but is most often described as the time between a command change, andthe time when the resulting actuator output reaches that command.

As illustrated in FIG. 11, a response time of a physical system iscommonly characterized as the time between the command change (t0) andthe time the output reaches 90% of its steady-state value as a result ofthat command change (t90).

Many common types of actuators can be characterized at least as asecond-order system, where the force or torque output of the actuator,divided by the commanded input, can be characterized as a function offrequency by the following equation

$\frac{Response}{Command} = \frac{gain}{s^{2} + {2{\xi\omega}\; s} + \omega^{2\;}}$

Where s is the complex frequency variable, ξ is the system damping, andc is the natural frequency of the system. While a second-order systemhas been described above, it should be understood that this has beendone for modeling convenience and other models including higher ordermodels might also be used.

An exemplary Bode diagram is presented in FIG. 12 and illustrates thepredicted frequency response for a simple second order system.

As an example, in an electro-hydraulic active suspension actuator,including an electric motor, operatively coupled to a back-drivablehydraulic motor-pump, and coupled to a hydraulic piston, the system canbe characterized through its reflected inertia, its system compliance,and the inherent system damping.

The system's transfer function now becomes

$\frac{Force}{Torque} = \frac{n}{s^{2} + {2\; B\sqrt{\frac{K}{J\; n^{2}}}s} + \frac{K}{J\; n^{2\;}}}$

Where s is again the complex frequency vector, B is the inherent systemdamping, 1/K is the total compliance (i.e. the inverse of the systemstiffness K), J is the total system inertia, and n is the motion ratio.Typically, the ratio

$\sqrt{\frac{K}{J\; n^{2}}}$

Without wishing to be bound by theory, this ratio typically is definedas being equal to 2πf where f is the natural frequency. The ratio isalso defined as the frequency at which the total kinetic energy and thetotal potential energy in the system are equal in magnitude and can thustrade off during the response of the system to an input or adisturbance. Additionally, it can be shown that the response time of asecond order system is directly proportional to the natural frequency,and that the response time increases with the system damping while theovershoot decreases. In a current active suspension system design, anatural frequency of about 30 Hz gives a response time of less thanabout 10 ms.

As noted above, in some embodiments, response times for a hydraulicactuation system and/or an active suspension system may be less thanabout 150 ms to provide a desired performance, which implies a systemnatural frequency greater than about 2 Hz, or a product of systemcompliance times reflected system inertia, or alternatively a ratio ofthe reflected system inertia to the system stiffness, of less than about0.0063.

Example: Natural Frequency Design Variations

Tables I-III present the ratio of reflected system inertia to systemstiffness for natural frequencies ranging between about 2 Hz to 100 Hz.Additionally, the tables present different design variations for thedesired natural frequencies given a particular reflected system inertia,stiffness, and/or motion ratio. Specifically, Table I presentsvariations in system stiffness for a given reflected system inertia of20 kg for various natural frequencies. Table II presents variations insystem inertia for a given motion ratio of 600 radians/m and a systemstiffness of 5×10⁵ N/m. Table III presents variations in motion ratiofor a given system stiffness of 5×10⁵ N/m and system inertia of 5×10⁻⁵kg m². While particular exemplary combinations of these design criteriaare presented below, it should be understood that the disclosure is notlimited to only these parameters and that systems including systeminertias, motion ratios, and stiffnesses both greater than and less thanthose presented below are also contemplated.

TABLE I Natural Freq. (Hz) Jn²/K (s²) Jn² (kg) K (N/m) 2 6.3E−03 203.2E+03 5 1.0E−03 20 2.0E+04 10 2.5E−04 20 7.9E+04 20 6.3E−05 20 3.2E+0530 2.8E−05 20 7.1E+05 40 1.5E−05 20 1.3E+06 50 1.0E−05 20 2.0E+06 1002.5E−06 20 7.9E+06

TABLE II Natural Freq. (Hz) Jn²/K (s²) n (rad/m) K (N/m) J (kg m²) 26.3E−03 600 5.0E+05 8.8E−03 5 1.0E−03 600 5.0E+05 1.4E−03 10 2.5E−04 6005.0E+05 3.5E−04 20 6.3E−05 600 5.0E+05 8.8E−05 30 2.8E−05 600 5.0E+053.9E−05 40 1.6E−05 600 5.0E+05 2.2E−05 50 1.0E−05 600 5.0E+05 1.4E−05100 2.5E−06 600 5.0E+05 3.5E−06

TABLE III Natural Freq. (Hz) Jn²/K (s²) K (N/m) J (kg m²) n (rad/m) 26.3E−03 5.0E+05 5.0E−05 7962 5 1.0E−03 5.0E+05 5.0E−05 3185 10 2.5E−045.0E+05 5.0E−05 1592 20 6.3E−05 5.0E+05 5.0E−05 796 30 2.8E−05 5.0E+055.0E−05 531 40 1.6E−05 5.0E+05 5.0E−05 398 50 1.0E−05 5.0E+05 5.0E−05318 100 2.5E−06 5.0E+05 5.0E−05 159

While the present teachings have been described in conjunction withvarious embodiments and examples, it is not intended that the presentteachings be limited to such embodiments or examples. On the contrary,the present teachings encompass various alternatives, modifications, andequivalents, as will be appreciated by those of skill in the art.Accordingly, the foregoing description and drawings are by way ofexample only.

What is claimed is:
 1. An actuation system comprising: a hydraulicactuator including a first volume separated into an extension volume anda compression volume by a piston slidably received in the first volume;a hydraulic motor-pump in fluid communication with the extension volumeand the compression volume of the hydraulic actuator to controlextension and compression of the hydraulic actuator, wherein uponoperation of the hydraulic motor-pump in a first direction, fluid flowsfrom the extension volume to the compression volume and upon operationof the hydraulic motor-pump in a second direction, fluid flows from thecompression volume to the extension volume; and an electric motoroperatively coupled to the hydraulic motor-pump, wherein the actuationsystem has a reflected system inertia and a system compliance, whereinthe system compliance is between 1/(7.9E+06) m/N and 1/(3.2E+03) m/N,and wherein a product of the system compliance times the reflectedsystem inertia is less than or equal to 0.0063 s².
 2. The actuationsystem of claim 1, wherein a product of the system compliance times thereflected system inertia is greater than or equal to 2.5×10⁻⁶ s².
 3. Theactuation system of claim 1, wherein a response time of the actuationsystem is between 10 ms and 150 ms.
 4. The actuation system of claim 1,wherein a natural frequency of the actuation system is between 2 Hz and100 Hz.
 5. The actuation system of claim 1, wherein at least one of thehydraulic motor-pump, and the electric motor are remotely locatedrelative to the hydraulic actuator.
 6. The actuation system of claim 1,wherein a pressure of the hydraulic actuator is substantially controlledby the hydraulic motor-pump operatively coupled to the electric motor.7. The actuation system of claim 1, wherein the motor input is at leastone of motor position, voltage, torque, impedance, frequency, and speed.8. The actuation system of claim 1, further comprising a controllerelectrically coupled to the electric motor, wherein the controllerapplies a motor input to the electric motor to control the hydraulicactuator in at least three of four quadrants of a force velocity domainof the hydraulic actuator.
 9. The actuation system of claim 8, whereinthe hydraulic actuator is controlled to operate in all four quadrants ofthe force velocity domain of the hydraulic actuator.
 10. The actuationsystem of claim 8, wherein the four quadrants of the force velocitydomain include compression damping, extension damping, active extension,and active compression.
 11. The actuation system of claim 1, whereinpower is applied to and consumed by the electric motor only duringactive extension and/or active compression.
 12. The actuation system ofclaim 1, wherein the hydraulic motor-pump operates in lockstep with thehydraulic actuator.
 13. The actuation system of claim 1, wherein theelectric motor is constructed and arranged to be operated as agenerator.
 14. The actuation system of claim 13, wherein the updatefrequency of the motor input is less than 1 kHz.
 15. The actuationsystem of claim 14, wherein an update frequency of the motor input isgreater than 0.5 Hz.
 16. The actuation system of claim 1, wherein thehydraulic actuator, hydraulic motor-pump, and electric motor, areintegrated with a single housing.
 17. The actuation system of claim 1,where the hydraulic actuator is constructed and arranged to be coupledto at least one of an excavator arm, a control surface of an airplane, afork lift, a lift boom, and an active suspension system.
 18. Theactuation system of claim 1, further comprising one or more valveslocated between the hydraulic actuator and the hydraulic motor-pump. 19.The actuation system of claim 1, wherein in at least one mode ofoperation the motor-pump is controlled to generate a pressuredifferential that acts on the piston to produce a force in a directionof motion of the piston.
 20. The actuation system of claim 1, whereinupon operation of the hydraulic motor-pump in the first direction, fluidflows from the extension volume to the compression volume through thehydraulic motor-pump, and wherein upon operation of the hydraulicmotor-pump in the second direction, fluid flows from the compressionvolume to the extension volume through the hydraulic motor-pump.
 21. Anactuation system comprising: a hydraulic actuator including a firstvolume separated into an extension volume and a compression volume by apiston slidably received in the first volume; a hydraulic motor-pump influid communication with the extension volume and the compression volumeof the hydraulic actuator to control extension and compression of thehydraulic actuator, wherein upon operation of the hydraulic motor-pumpin a first direction, fluid flows from the extension volume to thecompression volume and upon operation of the hydraulic motor-pump in asecond direction, fluid flows from the compression volume to theextension volume; and an electric motor operatively coupled to thehydraulic motor-pump, wherein the actuation system has a reflectedsystem inertia and a system compliance, wherein the reflected systeminertia is between 1.26 kg and 3168 kg, and wherein a product of thesystem compliance times the reflected system inertia is less than orequal to 0.0063 s².